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By L. F. Moran

Rod Mill Grinding is an important and fundamental step of the concentrating process in Marcona Mining Company's plants at San Nicolas Bay, Peru. This Paper summarizes experience in regard to consumption and specifications of grinding rods based on twelve years operation of the grinding circuits. Marcona operates a Plant complex producing 10 million tons per year of beneficiated iron ore products including pellets, sinter feed concentrates, high grade concentrates as slurry and filter cake. Processing capacity is 15 million tons per crude ore per year of which 13 million are around in rod mills. A continuous testing program was carried out over the years. Initial studies of daily production operations gave indications of poor grinding rates in relation to mill size and power consumption, with a high rate of broken liners and rods. The broken nieces of rod were not automatically expelled and further interfered with grinding efficiency, while replacement of liners caused unwarranted do n tire. Objectives were to improve all phases of the Process by studying the effects of changes in rod diameter, length, alloy constituents, and volume and weight of rod charge.

Jan 1, 1975

By James K. A. Harral

The growing national concern over energy has aroused a great deal of interest in the most efficient and least costly way to use our remaining fossil fuel reserves. A number of studies have been published which compare the overall thermal efficiency and cost of gas and electric energy. These studies have been carried out by a wide variety of organizations including Oak Ridge National Laboratory, The Rand Corporation, The Stanford Research Institute, and The Institute of Gas Technology. This paper is an attempt, by PGandE, a large combined gas and electric utility serving most of the northern and parts of central California, to compare the cost and efficiency of gas and electric energy for certain residential appliances using actual operating data and financial statistics for the year 1974, and thereby develop some guidelines for future energy developments utilizing these limited fossil resources. The appliances chosen for the study were kitchen ranges, clothes dryers, hot water and space heaters. These appliances were selected because they can be served with either gas or electricity and they account for approximately one-third of PGandE's total residential electric sales and nearly all of PGandE's residential gas sales.

Jan 1, 1976

By D. J. Frey

While costs of most commodities and services have increased markedly over the past 25 years, the cost of electricity has steadily declined. One of the reasons for this price decline is the improved efficiencies of generating plants which is shown in Fig. 1. 1,2 Another reason for this is the decline in coal production costs. Efficiencies for the best plant increased from about 32 percent in 1540 to about 40 percent in 1962 and then decreased slightly to 38 percent in 1965. The increase in efficiency for all plants (US average) has been even more notable, progressing from less than 15 percent in 1940 to about 32 percent in 1965. The chief reason for the improved efficiency is the change in operating steam temperatures. These increased about 12 F per year until 1200 F was reached in 1962. At this high temperature excessive corrosion of super-heater and reheater tubes was experienced and steam temperatures were dropped back to 1050 F and even 1000 F in some cases. To successfully compete against other energy sources for generating electricity, this corrosion problem must be solved so that operation at higher temperatures and thus, increased efficiencies will be possible.

Jan 1, 1967

By S. A. Braley

Water is our most important natural resource, for without it there is no life. It is also the principal natural resource for all manufacturing processes, in particular for the development of power. For these reasons it is essential that water be protected and conserved, with the realization that its quality 18 as important as the water itself. A significant factor in the quality of ground water is the mining of coal -- that other main ingredient of Power. In the mining of coal it is necessary to disturb the geological strata overlying or adjacent to the coal seam. This procedure not only releases water from water-bearing strata or underground aquifers but also exposes other minerals which eventually become the source of pollution or deterioration of the released water as well as of the surface stream into which It is discharged It is then evident that in attempting to utilize one essential natural resource there is degradation of the quality of the other. Many selfishly assume that the principal function of a stream is fishing and recreation, but the real function is the support of industry and agriculture upon which civilization is dependent.

Jan 1, 1959

By L. C. Morales

Mexico has an area of about 2 million km2 (772,260 sq miles), with volcanic activity, large shores and mountainous areas reaching as high as 6000 m (19,680 ft) above sea level. These conditions are favorable for most mineral deposits, some of commercial value and others as a source of mineral samples. In addition to its vast mineral wealth, Mexico has another valuable asset in its people. Even before the discovery of America, natives were successfully mining metals. During the colonial days, the mineral deposits were mined to increase the wealth of Spain. All this experience was passed from generation to generation. It created a tradition of mining and minerals processing engineers that currently accounts for about 182,000 people supported by mining-related activities. Nonmetallic minerals in Mexico have been mined by natives since the early days. They knew the value of kaolin clays for pottery, as evidenced by archeological findings. This experience was also passed from generation to generation and has become recognized worldwide as ceramic wares of high quality. The Talavera ceramic from Puebla is an example of family traditions many generations old.

Jan 1, 1994

By J. I. Adetunji

Mining activities usually affect the soil, subsurface layers, water resources, the atmosphere and in general the lives of the people. The effects can be mechanical, biological, ecological and economical in nature and these effects can be characterized by their intensity, frequency, duration and scale. In Oyo State, Southwestern Nigeria efforts are being made to employ a sustainable method in the exploration and exploitation of abundant industrial minerals present in the state. The minerals exploited include talc, clay, marble, sillimanite, tantalite, niobium, beryl, tourmaline aquamarine, rock aggregates, etc. Results of this sustainable approach show that the environmental impacts of surface and underground mining of industrial minerals are not spread far beyond the mines site acreage. More lands are being reclaimed, the amount of dust released into the air has been minimized, the quality of sewage waters produced during operations are minimized, top soils removed during subsurface mining are preserved, the tonnages of minerals exploited are being monitored and controlled. All these point to a positive development in practicing sustainable methods in mineral exploitation to meet the developmental needs of the Oyo State at present and to conserve for the future.

Jan 1, 2003

By J. Nelsen

Social License to Operate continues to emerge as a paradigm fundamental to sustainable mineral resources development. It relates to a set of concepts, values, tools, and best practices that represent the view of reality held by each participant (industry and stakeholders). It enables a forum for negotiation through which all parties involved are heard, understood and respected. The exploration phase of the mine life cycle is generally the initial contact with local communities and forms the cornerstone for effective communication and trust building. This paper presents the development of a mineral exploration template, based on field studies, aimed at assisting exploration personnel to establish effective communications and engagement with local communities within a process to build a Social License. The template aims to provide practical assistance in conducting situational analysis - a process of examining and mapping a situation, its elements and their relations - in order to acquire knowledge and understanding of a project, locale and region. Situational analysis is the ?full situation of inquiry?, going beyond just ?knowing the subject? to being fully situated. It forms the initial foundation for a planning process presented in the paper that prepares for a strategy of initial engagement and consultation.

Jan 1, 2007

By W. B. Beerbower

Resin bolting has enjoyed wide acceptance for coal mine roof support. Beginning in 1973, the first year of significant resin bolting in coal mines, we estimate that 2.5MM resin bolts were installed. This grew to 7MM resin bolts in 1974 and 13MM in 1975. Resin bolts are currently being used in over 300 coal mines throughout the major coal producing areas of the U.S. and barring major work stoppage we expect more than 17MM will be installed in 1976. Although not a cure-all, the number of unintentional roof falls occurring in many mines has been dramatically reduced as a result of converting to this "new" method of support. 1 The improved anchorage strength of resin bolts provides better roof support. (Slide #1) This anchorage strength provides a mechanism to resist changing roof stresses along the entire length of the fully grouted resin bolt, thereby assuring stabilization of rock strata over long periods of time. The ability to resist roof displacement is borne out by readings obtained from strain gauged bolts. These findings can be summarized as follows.2

Jan 1, 1977

By John A. DesLauriers

INTRODUCTION This paper will update the status of small sized tunnel boring machines used in both the Mining and Civil Industries. I will mention a) new developments in small size hard ground tunnel boring machines, b) review North American performance records of the Atlas Copco Mini/Midi Fullfacers, and c) compare relative costs in driving a 1200m (4000 ft) typical utility tunnel using a leased TBM versus the conventional drill and blast method. NEW DEVELOPMENTS JARVA MACHINES Of all small rock tunnel boring machines currently in use, the Jarva MARK VI and MARK VIII are receiving the most enthusiastic acceptance. These circular fullface borers using usually 15 inch single disc cutters (manufactured also by Jarva) are designed on the 'T' bracing principle. Previously, Jarva's line of tunnel boring machines, even their smallest, was designed on the 'X' or double diagonal bracing configuration with a gripper in each quadrant. In small tunnels where net room is so very important, the 'T' scheme with gripping only at the spring line nets precious room around the cutter unit for passage of men and supplies. It allows freer un-

Jan 1, 1981

By Ronald E. Heuer

It is not possible to accurately predict water flow into rock tunnels during construction, because all of the relevant factors cannot be accurately determined ahead of time. But an estimate is needed, because water inflow can be a major problem during construction, hence also a major concern for project design. There currently is no simple, generally accepted method of estimating inflow. This paper describes a semi-empirical method for estimating possible water inflow based on borehole water pressure test results, using correlations from previous tunnel experience. The method provides an estimate of percentages of tunnel length which will experience different intensities of long term steady state inflow, and provides an estimate of possible initial heading inflow. The method is applicable for distributed sources of water inflow due to rock mass features such as systems of joints and bedding planes, and accounts for different boundary conditions of water head and recharge. The metric system flow units used in this paper are liters per minute (L/min) and liters/minute/meter of tunnel (L/min/m), to be compatible with rock mass classification systems commonly used today.

Jan 1, 1995

By Peter J. Tarkoy

The art of predicting rock excavating machine performance has become increasingly detailed and refined. Researchers using laboratory experiments and machine manufacturers using field observations have identified and defined mechanisms of failure, rock and tool interaction, and relevant design principles affecting them. Concurrently, practitioners have developed index tests which reflect rock properties relevant to machine performance. Empirical relationships between index properties and machine performance (penetration rate, cutter consumption, and machine utilization) have been established from past experience and are currently used throughout the industry. Contractors have used such relationships for estimating throughout the world. The detail in which geological, geotechnical, test, and project data, empirical relationships, and construction experience are utilized, is limited by time constraints imposed by the bidding period. To fully utilize all available data, methods of analysis, and construction experience, a simple computer program was developed for a microcomputer costing less than $7500. As a result, 1. machine performance predictions are detailed & reliable, 2. construction alternatives may be examined, 3. anticipated conditions & performance are graphically, documented & easily comparable to those encountered, and 4. results include a listing of assumptions & results of performance analyses & a graphic performance summary.

Jan 1, 1979

By Andrzej Luszczkiewicz, Kazimierz S. Sztaba

Flotation tailing of Polish copper sulfide ores represents more than 90% of the mass of run-of-mine ore. The tailing contains mainly quartz, dolomite, clay minerals, traces of sulfides, and some accessory minerals. Almost all minerals of the tailing are well liberated and, therefore, any further beneficiation process applied to the tailing is expected to be inexpensive. In this work, results of investigations on utilization of flotation tailing using classification and gravity concentration are presented. It is shown that due to classification of flotation tailing in hydrocyclones, the coarse fraction becomes suitable material for gravity separation providing backfill material for underground mines as well as heavy minerals, a source of valuable rare elements. It was also found that heavy minerals separated by gravity methods contain a significant amount of rare elements such as zirconium, titanium, silver, rare earth metals, and uranium. The light fraction of the gravity separation contains well deslimed quartz particles and meets strict requirements for hydraulic filling material ked for structural support in underground mines. Evaluation of the cost of the proposed technology indicated that investment to implement the method would provide a return within 2-4 years.

Jan 1, 1995

By Kenneth F. Lane

In most industries it is normal commercial policy to try to gear production to the market. In times of scarcity output is pushed to its maximum and in times of glut output is reduced. Because of the effects of supply and demand, these times correspond to times of high and low prices respectively so the policy results in maximising long run total profits. Stockpiling is often an integral part of the policy. Stocks are accumulated during depressed market conditions and sold off when demand revives. This further increases the long run total profits. However, such policies cause violent fluctuations in short term profitability and impose severe financial strains. Indeed planning and implementing the policies are a central management concern which is often critical to the success of the industry. The mining industry is no exception and, for many raw materials, trying to balance supply with demand is an international problem. Stockpiling and restricted production agreements are common elements of policy. But very little attention has been paid to the one additional control which is unique to the mining industry, namely, the cut off grade. This neglect is apparent at all levels from individual mines to national economies.

Jan 1, 1979

By A. Chamaret

Minerals extraction is related to complex sustainable development issues that are subject to international and local controversies. Debates must be based on objective and comparative elements. Defining strong indicators for assessing impacts and performances of mining sites thus appears necessary to inform and support the decision-making process for stakeholders. Recently, many indicator sets have been developed on an international level based on top-down approaches, but they commonly lack legitimacy for stakeholders and adequacy to specific site issues. They thus need to be complemented by the consultation of local actors concerned by such mining activity, in order to define indicators that are closer to the needs and contexts of the specific sites. The question raised by this kind of top-down/bottom-up approach is how to organize and reveal the plurality of values and concerns associated with mining. Based on the principle of representative diversity, the approach undertaken at the Arlit uranium mines in Niger aimed at defining indicators that are understood and accepted by all actors. The aim was to measure the impacts and performances of mining sites in the four sustainable development dimensions, and at local, regional and national scales.

Jan 1, 2007

By Patricio A. Espinoza, Aldo Casali, Cristian Ardiles, Guillermo González

Cluster analysis is used to design grade soft-sensors in a rougher flotation plant and a ball mill overload soft-sensor. Soft-sensors are virtual sensors which either replace unavailable actual sensors or infer measurements for non existing sensors. In the case of the grade soft-sensors clustering serves to determine clusters of related operating points. To each cluster there corresponds an ARMAX model structure whose parameters are estimated using only the points in the corresponding cluster. Thus a much better correlation is found than if all the data points were used for a global model. The problem of identifying clusters when the measurement of the real sensor is not available is addressed. In the case of the overload soft-sensor, variables were selected which are related to overload, either from a phenomenological point of view or according to operator experience. Different clusters are formed, some of which are identified as determining an overload condition or a possibility of such condition. Each of these clusters has a set of operating conditions which suggests the corrective action to be taken when necessary. Both kinds of soft-sensors are tested with industrial plant data and promising preliminary results are obtained.

Jan 1, 1995

By Ronald C. Bethard, Kenneth W. Ely

The liberation of methane during underground coal mining causes serious safety concerns. During a mining cycle, with mechanized mining equipment, thousands of cubic feet of methane are released from coal seams, discharged to return air courses, and vented to the atmosphere through mine fans. This has been the traditional way of removing the explosive hazards of methane gas from the mine. Through horizontal and vertical degasification techniques, this hazard can often be handled in an equally safe and much more profitable manner. Basically, degasification allows for the controlled reduction of inseam methane content of coal prior to its mining. It is the responsibility of mine management to evaluate these degasification programs and ensure that the program itself does not introduce some new risk to the mining process. The removal of methane gas from underground coal mines using horizontal and vertical degasification is a relatively new concept. Products and systems used in degasification continue to evolve. Site conditions vary also, so no one system or equipment can be said to be the safe answer for degasification in all situations. A constant process of cooperation and evaluation by mining and degasification management should result in a safer and more profitable mine.

Jan 1, 1989

By J. Twining, V. Nguyen, J. Perera

A computer code for ecological risk assessment (ERA), AQUARISK, has been developed and applied to evaluate the likelihood of biotic detriment due to exposure to acid rock drainage (ARD) from the Burkunga mine site in Australia Stream water quality monitoring data were used for the assessment and were compared with a) national water quality guidelines, b) literature derived ecotoxicology data and c) biological monitoring data. With bioavailability calculations, the code predicted that, for metals exceeding the guidelines, 44% of macroinvertebrate species above the mine and 100% below the mine would be adversely affected by the metals in the stream. This compares reasonably and conservatively with biological monitoring that showed observed reductions of 41% and 85% of species respectively at each site. Using literature data for macroinvertebrates to predict impact produced similar estimates to using data for all taxa. Use of speciation modeling also lessened the degree of reduction in the median water metal concentrations required to achieve acceptable impact (measured either by exceedence of criteria or by species likely to be affected) by a factor of 75%. This result implies significant economic and management benefits in relation to remedial engineering or water treatment options for sites.

Jan 1, 2000

By Francisco J. Escandon V.

Numerous lead-zinc-barite-fluorite ore deposits, with simple mineralogy and roughly concordant with bedding, are found widely distributed all over the world, having been denominated and well described as "stratiform deposits" or "strata-bound ore bodies", not having any genetic relationship. During several years, its origin has been discussed, without getting to general agreement regarding the main mining districts of this type. Through studies made of large stratiform deposits in the United States, Europe and Russia, it has been found that there are, within this classification, syngenctic diagenetic and epigenetic ore bodies. During the Symposium about the genesis of the stratiform lead-zinc-fluorite-barite deposits, carried out in New York in 1966, Frank G. Snyder (1), presented an excellent analysis of the theories of the origin of these deposits and of the evaluation of the criteria regarding classification. As per his definitions (Table 1), "a deposit is syngenetic if formed by processes similar to and simultaneously with the enclosing rock, epigenetic if introduced into a pre-existing rock and a diagenetic origin implies deposition of metals with the host sediments but with recrystallization, rearrengement and limited migration".

Jan 1, 1974

Not quite a year ago, during a speech to a group of mining professionals in Washington, DC, the subject centered around the long-range importance of conducting research projects and how much that research needs to specifically apply to health and safety matters in our industry. The point was made about the critical need to work together with government, private industry, labor organizations and academia speaking with a unified voice as we all march into the future together. The fundamental benefits of competitive research were mentioned --to improve our quality of life, to develop our energy resources, to achieve a safe and healthy environment and to ensure long-term economic growth. Very importantly, emphasis was given to the natural link that makes my agency, the Mine Safety and Health Administration, and the National Institute for Occupational Safety and Health --NIOSH --the beneficiaries of each other's findings. Unquestionably, there are lines of separation. The main responsibility of the agency I represent, MSHA, is enforcement of the nation's mine safety and health laws. But we also have an additional responsibility and that is to coordinate and give priority to research in a never-ending hunt for answers.

Jan 1, 1999

By Ernest Y. Baafi

This paper describes the results of a series of comparative studies in which polygonal, IDS, and kriging were compared for their local estimation accuracy. The specific objective of this study was to determine the impact that the particular nature of the mineralization has on the results of such comparative studies. The study was performed on simulated coal deposits and the evaluation parameter chosen was the coal thickness. For this study, many conditionally simulated deposits having different degrees of seam thickness continuity were first developed. Each simulated deposit covered an area of 30,000 ft x 30,000 ft which was, in turn, subdivided into 100 mine planning blocks of 3,000 ft x 3,000 ft in size. Thickness estimation was made for these mine planning blocks using surrounding DDH assays. In all cases tested, e.g., from a perfect continuity to a complete lack of continuity in coal seam thickness, kriging gave the best estimates among the three, followed by IDS and polygonal methods. As expected, the relative efficiency (i.e., superiority) of kriging over other estimators was highly dependent on the nature of mineralization.

Jan 1, 1982