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By M. E. Rossi

Reconciliation of long-term, block-model reserves and mine production frequently shows significant discrepancies. This reconciliation can be done comparing the long-term, block-model reserves against a grade control model (a model based on blast holes or production data). In this article, this is called an Fl factor for tonnages, grade and ounces. This reconciliation should also be done by comparing the grade control model to the mill feed (or loaded to heaps) tonnages, grades and ounces (F2 factor). The long-term model usually contains blocks with dimensions larger than the size of the selective mining unit (SMU) of the operation. The smoothing effect of an estimator, such as kriging, will generally result in a grade-tonnage curve that does not match the grade-tonnage curve of the SMUs to be recovered. This problem is partly to blame for the reconciliation discrepancies found. In addition, in-pit perfect selection is impossible. Therefore, the grade-tonnage predictions based on blastholes also need to be assessed - considering unplanned dilution and the errors of estimation of the grade control model. This article focuses on using conditional simulations to assess the uncertainty of the predicted grade-tonnage curve in terms of minable reserves and in the framework of long-term mine planning. Quantifying the uncertainty in no uncertain terms is done in conjunction with a popular pit optimizer. It yields several possible minable reserves and several possible minable tonnages and grades, per pit shell or scheduled phase. This is a step further from the usual sensitivity analyses that are performed for deposit evaluation or development planning. Specifically, this approach takes into account the volume-variance relationship, the selectivity of the mining operation and the planned and unplanned dilution. It also carries the local uncertainty implicit in grade estimation into the mine design and mine planning phases. The estimation of recoverable reserves revolves around estimating the block distribution of metal grades from the drill hole information available, typically composites of a fixed length. Ideally, this estimation should accurately predict the ore sent to the processing facilities of an operation. Here are some definitions used in this article: ? Recoverable reserves are those where an attempt has been made to estimate the actual distribution of grades (usually by a block model) that would be found in the ground at the time of mining, relative to the mine equipment size and other operational characteristics of the mine SMU. In particular, it incorporates the effect of internal dilution for each block how the grade distribution changes in variability when comparing a composite grade distribution to the "mining unit" grade distribution. In geostatistical jargon, this is known as "change of support effect," or volume-variance effect. ? Minable reserves are those recoverable reserves defined by a mine plan. In an open-pit scenario, they would incorporate pit optimization in addition to the sequencing and scheduling of production through mine life. ? All other block model estimates from drill hole data that do not explicitly attempt to estimate or measure the volume-variance effect are called in situ. It can be argued that these models may be inappropriate tools for predicting the grade-tonnage curve of the material to be sent for processing (minable reserves). The purpose of estimating recoverable reserves can be thought of as estimating the appropriate amount of dilution that should be incorporated into the model so that it adequately predicts (long-term and on average) the grade-tonnage curve of the ore sent to the processing facilities (mean grades and ton-

Jan 1, 1999

By Ziyan Ouyang, Haotian Zheng, Spencer Quiel, Mike Mooney, Clay Naito

This paper summarizes the results of an experimental program conducted to characterize the moment-rotation behavior of skewed flat radial joints from large diameter (45 ft) tunnel lining. Both positive and negative joint moment-rotation behaviors were measured experimentally using two-segment joint combination assemblies. The results are compared to closed form methodologies used by designers, e.g., the Janssen method. The differences in observed and model behavior are discussed within the context of design practice.

Jun 23, 2024

By Lit-Mian Chan, David H. Carlson, John H. Johnson

This paper presents an apparatus and procedures to implement a methodology for controlling ambient air quality in a confined working environment, such as an underground mine, an underground storage area, or a tunnel. The air quality control methodology is directed at limiting the quantities of exhaust pollutants emitted by diesel-powered vehicles into the confined space by identifying vehicles that are excessive polluters. The methodology is based on tailpipe and ambient air measurements in the confined space, and the ambient air threshold limit values (TLVs) for the various diesel exhaust pollutants. The methodology consists of two computational methods; a deterioration criteria computational method to identify excessive polluting vehicles, and an engine performance computational method to determine engine performance and to provide information needed to diagnose engine faults. The methodology is designed for implementation in conjunction with a preventive maintenance program. The first part of the paper describes the mine air and tailpipe emissions measurement apparatus and techniques used to obtain data. This is followed by sections discussing the deterioration criteria and the engine performance computational methods. A section discussing some common engine emissions-related faults is also presented. Lastly, a proposed procedure to implement the methodology including a possible hierarchical structure for mine personnel involved to implement the procedures is presented.

Jan 1, 1993

By S. K. Kawatra, S. J. Ripke

Iron ore pellets use bentonite clay as binder at dosages from 0.5to 1.0% (10 to 20 pounds per ton) of moist iron ore concentrate. Bentonite is typically shipped hundreds of miles from Wyoming to the Lake Superior iron ore district. It is therefore best to know how effective a bentonite will be before it is shipped and used to bind concentrate into pellets. Current tests of bentonite effectiveness include: plate water absorption, methylene blue uptake, free swell, exchangeable cations, and glycolated layer expansion. However, these tests have many disadvantages: First, they only measure the ability of a bentonite to expand, disperse, or absorb, not how well it will bond. Second, most of the tests require up to 20 hours to perform. Bentonite only has a few minutes to interact within the concentrate before it is indurated (sintered). These long-term tests may not reflect the true behavior of bentonite. Third, the tests are tedious and often results are inconsistent between different iron ore concentrates, labs, and technicians. Fourth, some of the testing equipment is difficult to procure. Fifth, procedures are often difficult to standardize. In this paper, the Binder Effectiveness Strength (BESt) test to evaluate binders for iron ore pellets is presented that: measures the ability of bentonite to bond, requires only about two hours to complete, is simple and reproducible, and utilizes readily available equipment that has been standardized for decades.

Jan 1, 2003

By John W. Rozelle, David S. Bolin

INTRODUCTION During the normal course of a mining project, a feasibility study will be prepared that addresses all the aspects of the project including geology and mineral inventories, mining and geo- technical, metallurgical processing, infrastructure, environmental considerations and economic analyses. These studies are prepared for various reasons. Occasionally, a feasibility study will be prepared solely for use within a company as justification for development expenditures, however, these documents are frequently submitted outside the company either to raise funds from financial institutions or from public financing on one of the various securities exchanges. Mineral industry consultants are often called upon to participate in the preparation of feasibility studies or to conduct an independent audit and review of an internally prepared study. As the recoverable mineral resources form the foundation upon which the balance of a feasibility study is based, including the economic analysis of the project, the resource aspect of the study is examined very carefully by financial and securities organizations. The balance of this discussion is directed toward the various geological and resource estimation aspects of feasibility studies that experience has shown to be of particular importance. Much of this discussion will be directed toward open pit gold operations, although the principles are applicable to any type of deposit. 2.0 GEOLOGIC RESPONSIBILITIES IN FEASIBILITY STUDIES The principal geological effort in the preparation of a feasibility study is generally dedicated to the following areas: - Preparation of Geologic Reserve/Resource Estimates - Condemnation of Sites for Facilities, Access Roads, Leach Pads, Waste Dumps and Tailings Disposal - Collection of Geotechnical Data - Provision of Mineralogical and Petrological Data Pertinent to Metallurgical Processing - Selection of Appropriate Bulk Sampling Sites for Collection of Metallurgical Samples Each of these items will be addressed in detail in the following sections. 3.0 RESERVE/RESOURCE ESTIMATION An ore reserve estimate consists of the determination of a volume, or tonnage, and a grade for the deposit. There are numerous cases in the mining industry of projects that have experienced severe difficulties when operational ore grade, tonnage or metallurgical amenability have proven to be deficient compared to predicted estimates. An error in estimation of tonnage generally leads to more long term problems affecting mine life and production schedules. However, a significant error in the estimation of grade, particularly if mined grade is lower than anticipated, can have an immediate, and often disastrous, effect upon a project. The geologic preparation leading to an ore reserve estimate generally follows a logical sequence familiar to

Jan 1, 1987

By John M. Wootten

The development of new coal markets is -t upon the ability to utilize coal in an environmentally acceptable and economically viable fashion. Foremost in the concerns about coal utilization is the impact its combustion has on air pollution. Concerns over environmental issues, such as acid rain, are currently one of the major impediments to the development of new coal markets. The Department of Energy and the Synthetic Fuels Corporation are addressing certain aspects of the development of new technologies for the utilization of coal. However, at the present time, there is a void in the new technology development process. That void is the step from proof- of-concept to commercial demonstration. Congress has established the Clean Coal Technology Fund at a level of $750 million to fill this void. The Department of Energy, in a solicitation of interest, received over 175 proposals for commercial demonstrations of clean coal technologies. A review of these solicitations indicates that $1.2 billion worth of research could be accomplished with a federal cost sharing of $425 million or 35 percent of the total. Industry has indicated, through this response, its willingness to invest its limited funds on projects it feels have the greatest potential for the clean use of coal. What must now occur is that Congress must appropriate the monies from the fund to initiate the commercialization of these clean coal techno1ogies.

Jan 1, 1986

By Erich U. Petersen, J. B. Hiskey, William J. Tafuri, Donald M. Hausen, X. H. Jiang, Douglas N. Halbe, G. Ramadorai

The extraction of gold from chloride solutions with activated carbon is examined. It is shown that the uptake of gold by activated carbon from chloride solution follows a mechanism whereby gold is reduced to the metallic state. Metallic gold appears as deposits both on the carbon surface and in pore space within the carbon particle. The deposition rate is dependant on the carbon particle size and pH. At low initial gold concentrations, the initial rate is insensitive to gold concentration. Sodium hypochlorite exhibits an adverse effect on the reduction reaction. The overall loading and initial rate of reduction are both decreased in the presence of NaC10. The effect of iodide on the loading of gold was also examined in an attempt to overcome the superficial deposition of gold on carbon.

Jan 1, 1990

By R. Flattery, Z. Agioutantis

Coal and rock pillar design is critical not only for mineral extraction but also for the safety of the mine operators. Pillar strength can be estimated through numerous empirical formulas that are available in the literature, which are typically based on a statistical analysis of case study data. The limitation of most of these equations is that they only considered the width to height ratio and in situ rock or coal strength for pillars in horizontal seams. The adoption of such equations to estimate pillar strength in inclined seams may overestimate the pillar strength and ultimately lead to a poor pillar design. This paper will discuss different techniques that can be used to estimate pillar strength in inclined seams as well as present preliminary modeling results for stress redistribution around inclined pillars. Factors in the parametric analysis include pillar shapes, geometry, and seam inclination.

Mar 2, 2022

The ever-increasing power (and decreasing cost) of computers has opened up substantial oppor¬tunities for 'Vision'-based systems in both on-line and off-line control. This paper reviews image analysis applications in use at the Julius Kruttschnitt Mineral Research Centre (JKMRC) for: •blast and mill feed size monitoring; •AG/SAG mill model-based control; •mineral liberation; and •froth flotation control. The SPLIT™ image analysis system is being used to estimate muck pile and ROM feed sizings. AG/SAG mill feed sizing is being used in a dynamic model for mill control. A new generation mineral liberation analyzer has been developed with Philips Electron Optics. The Philips-JKMRC mineral liberation analyzer offers a substantial improvement in resolution and speed over previous developments. While on-line liberation control continues to be something of a pipe dream, measuring liberation "one shift behind" is now feasible. A robust instrument has been developed to measure flotation froth bubble size and velocity. The instrument also derives a parameter that allows different froth textures to be distinguished. The instrument has been used for on-line control in coal and sulfide flotation. For coal froth, an online ash estimate has been achieved at one site and is being tested at other sites. Overall, image analysis is finding many applications in mineral processing and control.

Jan 1, 2000

By Richard D. Grove

The on-stream analysis of phosphorus and silica has not been possible by XRF techniques and only recently has some success been indicated with quantitative XRD for P. Yet there has been a recognized need for an on-stream analysis of P and acid insoluble to permit the automatic control of phosphate rock flotation plants which produce some 30-40 million tons of concentrate each year in the southeastern U.S. IMC Fertilizer, Inc., the largest U.S. phosphate rock producer, embarked on a program to develop such an on-stream analysis capability several years ago. Following many months of lab and prototype development, the first commercial installations started in December 1986 and now have completed some 400,000 analyses with surprising accuracy, precision and reliability. The use of these devices in the improved control of the phosphate flotation plant is currently receiving some very serious attention at IMC.

Jan 1, 1989

By Leopoldo Cortez, Fernando Durão

The dynamic control of a froth flotation section is simulated through a neural network feedback controller, trained in order to stabilize the concentrate metal grade and recovery by applying random step changes to the feed metal grade. The results of the application example show that this controller seems to be sufficiently robust and a good alternative to handle a non-linear process.

Jan 1, 1995

By Marvin Barnes

The Sacaton mine is a relatively new open¬pit copper mine owned by Asarco, Inc., which has been in production only a few years. The mineral deposits consist of two ore zones; a western, near-surface zone minable by open-pit methods, and a deeper eastern zone which will have to be mined underground, probably by block caving. The copper deposits are related to small quartz monzonite intrusives implaced into Precambrian granites. Both rock types act as hosts for the copper mineralization, which has been secondarily enriched sufficiently to constitute ore. In the western zone the enriched supergene chalcocite has been subjected to postenrichment oxidation processes with partial destruction of the chalcocite blanket. The deeper eastern chalcocite zone has not been as severely affected by later supergene processes. Several mineralogical populations are represented in the total copper deposit. Leached capping overlies the chalcocite enriched zone, and in the western ore body there is a very irregular interface between the leached and enriched zone, which is complicated by oxide copper minerals irregularly distributed. Primary lower-grade chalcopyrite mineralization occurs below the enriched zone. When mining commenced near the top of the enriched zone, considerable difficulty was encountered in correlating the actual grade of ore in place with the estimated grade of the mining blocks. The mineralogical complexity and fairly wide spacing of diamond drilling made reliable grade estimation of individual ore blocks a difficult procedure.

Jan 1, 1979

By Finn E. Bronner

HISTORICAL PERSPECTIVE "Blessed be the Lord my strength, which teacheth my hands to war and my fingers to fight." Thus sang David three thousand years ago, in tacit acceptance of the condition of war, and in praise of the exceptional military skills with which this warrior king of Israel was endowed. He had cause to exult, for he had consolidated King Saul's conquests and added new ones of his own, not least of which was the capture of Jerusalem. David revealed in this operation that his mastery of the military arts embraced not only the weaponry and tactics of his day, but also strategy and that oldest of intelligence techniques: spies. The Jebusites, who built Jerusalem, had encompassed the city with the first of its many walls, but had neglected to incorporate the sole reliable water supply within its perimeter. This was Ain Gihon, today called the Fountain of the Virgin, which bubbled out on the east slope of Mount Ophel, one of the ridges on which Jerusalem was built, and drained eastward into the Kidron Valley. Water was brought into the city in the traditional manner: by women descending the stony trail outside the wall to fill their jars at the spring. But this essential daily activity was vulnerable to interruption by a hostile force outside the walls. To remedy this weakness, the Jebusites had driven a gallery from the spring a short distance into the water-bearing limestone under the city, and there cut a small collecting basin in the rock, a common way to develop springs throughout this arid region. But then the Jebusites dug a small vertical shaft from the roof of the gallery above the cistern upward about 15 m. From the upper end of this shaft, they constructed a narrow inclined tunnel with rock-cut steps leading up to the city streets. Thus the water supply could be reached even in time of siege.

Jan 1, 1979

By B. Cristol, G. Benier

Laboratory and pilot tests have shown that the grinding of some aluminas makes two populations appear : agglomerates’ and ultimate crystals’. Classical breakage functions (Size Mass Balance Method) aren't able to describe correctly this kind of grinding. So we have optimized a particular breakage matrix which takes into account the fact that the agglomerates can either be reduced in size or either be blown up to liberate the ultimate crystals. The models which were developed using this breakage matrix are in good agreement with the experimental results of the pilot tests. The industrial breakage functions were estimated from pilot breakage functions, using scale up prediction procedures and plant tests. The agreement between predicted and actual plant performance is excel1ent.A 20 % increase in capacity was predicted to be available by improving the grinding circuit classifier performances.

Jan 1, 1992

Rinker Materials Corporation (Rinker) operates construction aggregate operations in 15 states across the US. Thirteen of those operations are located in Florida, where Rinker produced approximately 40 million tons of aggregates in 2002. Because the deposits being mined in Florida are shallow sedimentary deposits of limestone and natural sand, with the deepest being approximately 75 feet deep, abundant acreage is mined annually. Rinker mines about 300 acres/year in Florida alone, and because there are so many wetlands and complete avoidance is nearly impossible, there are also wetland impacts. Thus, there is ample need for reclamation and mitigation, which presents an opportunity to involve local school groups with the planting and monitoring of these various projects. Rinker has successfully worked with a half dozen or so schools on these projects, involving students from grade school through college, with surprising success and outstanding results.

Jan 1, 2004

By T. J. McKeon

Gravity separators such as spirals are commonly used in multistage cleaning and scavenging circuits to improve the quality and recovery of concentrates produced in the industrial minerals industry. Unfortunately, field surveys suggest that many industrial operations are poorly configured in terms of equipment layout. This shortcoming can often be attributed to a failure by engineers to make use of fundamental process engineering tools for circuit design. One of the most important of these is linear circuit analysis. This powerful tool makes it possible to mathematically compare the relative efficiency of circuit configurations in advance of experimental testing. This article provides a basic review of the linear circuit analysis concept and discusses some of the key insights it provides for the layout of multistage circuits. An industrial case study is provided to show the tremendous impact that this process engineering tool can have on the design of multistage spiral circuits in a heavy mineral wet plant.

Feb 1, 2012

By S. S. Peng

Horizontal stress is an important factor that contributes to roof failure during longwall entry development, especially when the immediate roof is weak. In this paper, the effects of stress angle between the maximum horizontal stress and entry development and stress ratio of the maximum to minimum horizontal stresses on the stress distributions in the weak immediate roof of a three-entry system are analyzed using the finite element method. The results have confirmed that stress angle has a significant influence on the stress distributions. Generally, the three-entry system is in the worst stress condition when the stress angle is about 60° to 75° . The stress ratio has also some effects on the roof stresses.

Jan 1, 2000

By B. Howerton, M. M. Matlock, D. A. Atwood

In the Gold-Cyanide Process (GCP) the cyanide anions act to solubilize the gold and silver present in the ore, and mercury as well. The resulting mercury and cyanide rich effluent are serious health and environmental problems. Currently, there is no mercury treatment from the ore leach solution since there are no precipitating agents or other technologies which can be used effectively in the pH ~ 10solutions. Recently, however, we have developed a new chelate ligand that is impervious to this level of pH and it can be used to precipitate Hg from NaCN solutions. On an actual sample taken from an active gold mine the chelate selectively reduced the mercury level from 34.5 ppm to 0.008 ppm within 15 minutes. Importantly, the gold and silver levels remained unchanged throughout this process. Thus, the environmental impact of Hg released in the GCP can be drastically reduced. Moreover, with a mercury treatment technology now available it may be possible to change, or reinvent, the entire GCP process.

Jan 1, 2003

By V. K. Gupta

A detailed experimental study of the variations in grinding rate with particle size, particle load, ball diameter, ball load, mill diameter, and mill speed was carried out for a soft cement clinker and a hard cement clinker. The effects of the ball diameter, ball load, and particle load were observed to be material (hardness) independent, and those of the particle size, mill diameter, and mill speed to be material dependent. A sharp change in grinding behavior was observed for both the clinkers at about 150 µm size. Below this critical size: (1) the hardness difference between the two clinkers became insignificant, (2) variation in the grinding rate with particle size became markedly more pronounced, and (3) mill speed had little or no effect on grinding rate. The importance of these results in the context of process optimization and control is discussed.

Jan 1, 1988

By J. Lancaster

World demand of sulphur-in-all-forms (SAF), which in 1985 is estimated to total 57.5 million tonnes S equivalent, is expected to increase to 77.6 million tonnes S by the year 2000. Key factors are the evolution of sulphur demand in the USSR, China, and the developing countries notably India, Brazil, and the countries in North Africa and the Near East with vertically integrated phosphate industries. Brimstone will remain the dominant sulphurous raw material notwithstanding the progressive increase in the supply and use of sulphur in other forms resulting mainly from the enhanced recovery df pollution sulphur and the increased use of sulphur in pyrites in those countries with this sulphur resource. Sulphur demand for phosphate fertilizer manufacture is expected to have the main impact on world sulphur demand, but in contrast to the industrially advanced countries where non- fertilizer sulphur use is not expected to increase measurably, this demand sector is expected to be of some importance in those developing countries with dynamic economies and in the centrally planned economies of East Europe and the Far East.

Jan 1, 1986