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By Edward C. Dowling

Cleveland Cliffs and affiliated companies have established a commitment to the development and use of integrated process control. Substantial capital investments in process control, coupled with the dedication of human resources to effectively use the information, have generated meaningful business results. Improvements in productivity, operating costs and product quality have been realized. This paper presents an overall process control and information strategy, specific case studies, lessons learned and the current view of the next steps in the continued journey toward integrated process control and information management.

Jan 1, 2000

By Robert F. Conley

This paper describes attrition milling as exemplified in rotary and vibratory mills for ultrafine grin¬ding application Without attempting to narrate the differences between various devices, generalized differences between the broad categories of rotary and vibratory milling are presented and compared with the ball mill Applications of these mills for coal, limestone, kaolin, mica, talc and iron oxides are described giving specific differences of the mineral properties that affect their behavior in the grinding mills Where applicable, specific recommendations are provided for ultrafine grinding of various industrial minerals

Jan 1, 1983

By E. H. Ahrens

This paper deals with the responsibilities of an operating geologists and the relationship of operations to exploration. It should be of interest to those soon to enter the profession, those new to pining geology and as a review to more experienced geologists. Subjects discussed include detailed geologic mapping, sampling, core logging, assaying, selection of proper map scale, posting geological and assay data, section preparation, identification of ore controls, delineation of development drill targets and geologic hazards, models and the very important topic of salesmanship. Methods and ideas, proven valid in vein, pyrometasomatic replacement and porphyry copper deposits are presented. Hopefully, these will smooth the path for new members of our profession.

Jan 1, 1992

By Raj K. Rajamani, Ilesh M. Shah

Maintaining pH, a routine requirement in many industrial processes, is by no means trivial. The control is troublesome because of the inherent nonlinearity and frequently changing process dynamics. Many researchers in the past have investigated advanced on-line estimation and/or adaptive control techniques to overcome these difficulties. Most methods require the development of a complex mathematical model. The present work deals with the use of a simple and elegant method for pH control, based on the use of fuzzy logic. First, a standard fuzzy-logic controller is discussed, followed by a self-organizing controller. The latter algorithm generates a set of rules based on observation of the process. Thus it is a learning algorithm. The development and application of the algorithms to a laboratory acid-base neutralization experiment are presented. This elegant technique is powerful and deserves attention in mineral pro- cessing.

Jan 1, 1990

By Charles T. Staniek

Following a dragline relocation at Agrico's Fort Green phosphate mine in 1986, the recovery plant experienced a significant decrease in flotation performance. Through weeks of trial and error testing, we discovered we could restore recoveries by conditioning feed at pH's higher than we had used historically. The higher pH's essentially increased flotation cell kinetics, although we still do not understand the exact mechanism at work. Armed with new-found appreciation of pH modification, we initiated a program to determine the optimum modifier for us, from both a performance and environmental perspective. Environmental considerations were important because ammonia, the standard industry modifier, is a plant nutrient and higher usage rates could affect the quality, of our recycle process water. This paper describes the research and development work spanning a 3 year period that culminated in making a major change in our reagent suite when we replaced ammonia with soda ash on a permanent full-time basis.

Jan 1, 1993

By Juan P. Camus

One of the most important decisions in mine development is the selection of the mining method. Open pit or underground methods are selected depending on the shape of the deposit, and its position with respect to the surface. When the decision is not clear or evident, then the common rule is to compare underground and open pit projects to choose the one which yields the maximum return. However, in some circumstances' the best alternative is to start-up the operation with an open pit until a point where mine operating costs make more convenient to employ an underground method. In this case, the final pit limit is not directly related with commodity prices and its position is a funtion of capital and operating costs associated with both methods. The goal of this paper is a mans of establishing the proper ultimate pit considering a potential underground mine. The methodology is quite simple and can be implemented to work with a variety of available routines for pit optimization, such as Lerchs-Grossmann, floating cone, network flow and the Lemieux moving cone optimizing algorithm, which is the tool used by the author.

Jan 1, 1992

By P. Venkatraman, F. S. Knoll, W. S. Kow

Froth flotation is the most widely used technique for cleaning fine coal. This practice may change, however, with the development of enhanced gravity concentrators such as the Mozley Multi- Gravity Separator (MGS). The MGS is a flowing-film concentrator that utilizes centrifugal forces to improve the separation of flotation-size particles. In the present work, a pilot-scale test program was conducted to examine the effects of feed rate, feed solids content, wash water flow rate and drum rotation speed on the performance of the MGS. The test results indicate that the MGS effectively rejects high-density minerals such as pyrite, while ultrafine ash-forming minerals are removed less efficiently. A major advantage of the MGS is that high separation efficiencies can be realized without additional grinding, flotation reagents or heavy media. This article describes the working principles of the MGS and presents data obtained from recent pilot-scale test work.

Jan 1, 1995

By Ora H. Rostad

Some gold production was obtained from placer deposits in Puerto Rico during the period of Spanish colonial rule, but most of the gold was produced prior to 1536. There had been no significant hard rock mining, other than in quarries for road metal or construction purposes or for raw materials to make cement, prior to 1954 when the government of the Commonwealth of Puerto Rico recognized that changes in the mining code were necessary to stimulate exploration for metalliferous ore deposits. The Puerto Rican Legislature passed an act (No. 6), which was approved on Oct. 6, 1954, that reiterated that the title to all "commercial minerals" is vested in the Commonwealth of Puerto Rico. The act provided for the establishment of a Mining Commission, stipulated the power% with which the Mining Commission was vested, and provided that no one may dispose of "commercial minerals" in Puerto Rico without a Commonwealth grant issued on its behalf by the Mining Commission. Act No. 6 also provided for prospecting permits, mining leases, and grants. The Mining Commission, by authority granted to it by Act No. 6, adopted regulations effective Nov. 21, 1957, relating to prospecting, leasing, and producing commercial minerals in Puerto Rico. Royalty rates were also specified for various types of deposits at different annual tonnage production levels.

Jan 1, 1991

By S. Ash

Murray mine was one of the first Mechanized cut and fill underground gold operations in Northern Nevada. At the end of 2002 mine production began to decline and Murray entered a phase of remnant mining and began preparations to close down. The remaining mining took place along the ore waste boundary, in previously condemned areas, and in highly challenging ground conditions. To remain economically viable new techniques were implemented in operations, geology, engineering, and rock mechanics. These improvements pushed the edge of known and accepted mining practices and have allowed Murray to remain in operation today. History The Murray mine is located on the Jerritt Canyon property, which is located 45 miles north of Elko, NV in the Independence mountain range. Mining operations started at Jerritt Canyon in 1980 out of several open pits. In 1993 underground mining began in conjunction with a decline of surface mining operations. The transition from surface mining to underground mining moved the property into a new era. At the time there were limited examples of successful underground operations in the area from which to draw experience. Several mining methods were attempted with varying degrees of success and underhand cut and fill proved to be the most effective method. To date Murray has mined 1.2 million ounces at an average grade of .335 OPT utilizing this mining method.

Jan 1, 2006

By J. S. Walker

Public Law 95-87 enacted by Congress in 1977 and subsequent regulations require coal mine operators to predict the effects of mining on the environment prior to the start of mining. Prediction of the effects of mining on the local groundwater system is a difficult task due to its complex nature and the lack of detailed published information. An investigation of water level fluctuations in five we1 1s positioned over three consecutively mined longwall panels was initiated in conjunction with an intensive subsidence monitoring program. The purpose of this work was to provide detailed information which could be used to predict certain hydrologic effects of longwall mining in the Northern Appalachian Coal Region. The results of this case study indicate that water level fluct- uations in the local ground-water system above longwall panels is associated with subsidence and that the static water level will generally re- establish at or near the pre-mining elevation after mining is completed.

Jan 1, 1986

By O. Olajide, E. H. Cho

A laboratory study of the jigging process with Pittsburgh seam coal has been conducted. The laboratory-scale Baum jig used in this study was a McNally-Norton LO30X Right Hand Model Baum jig with an effective screen area of 0.186 m2 Feed material was prepared by selecting a size range from 6 mesh to 1.91 cm. Solid feed rates were 27.2 kg/min and 32.7 kg/min. Water flow rates were varied from 37.9 to 94.6 L/min. It has been found that smaller particles give higher values of density of separation and lower efficiency of separation. Increasing water flow rate increases the discharge rate of clean coal at a constant solid feed rate. It appears that the efficiency of separation increases by increasing water flow rate up to a certain value, and then levels off upon increasing the flow rate further.

Jan 1, 1988

By I. Nishkov, L. Alexandrova

The kinetics of froth flotation and the three-phase contact (TPC) parameters are studied at temperatures varying from 20°C to 40°C. The material floated consists of glass spheres and a quartz particles with various diameters. Dodecylamine hydrocloride (DDAHCI) is used as a collector. The equilibrium three-phase contact angle is measured with a microscope technique using the modified Mingins-Scheludko method. Using a Wilhelmy method, the temperature effect on the surface tension of the DDAHCI solution is determined. The formation of the thin film on a polished plate of vitreous silica and the expansion of TPC is monitored by means of a metallographic microscope and recorded on a attached camera at different temperatures. The experimental data show an intensification of the flotation kinetics at 30 and 40°C in the case of small particles. Such an intensification is not observed with the larger particles. The cause for intensification of the flotation kinetics is sought for in the dependence of the TPC rate of expansion and induction time on temperature.

Jan 1, 1995

By J. M. Mutmansky, Aiping Wang

This paper outlines the patterns of methane emission in both longwall and room-and-pillar operations and discusses the effects that these patterns have on the decision as to whether the methane is most economically handled by ventilation alone or by means of a methane-drainage system in addition to ventilation. The costs of handling the methane in the ventilation system and the costs of implementing the methane-drainage system are discussed, as well as the costs related to the production of coal. The important issues of production slowdowns and gasouts are also discussed, as well as the proper response of mine management to such a situation. Suggestions concerning the keeping of production records related to methane problems are made, and the justification for more intensive economic analysis of coalbed methane extraction and utilization is discussed

Jan 1, 2000

By B. Elevli, M. D. G. Salamon

Production scheduling of an open-pit mine is one of the most important steps in open-pit mining. The mine's production schedule defines the distribution of cash flows and, as a result, directly influences the net present value (NPV) and overall economic feasibility of a project. The need to plan and operate a mine with an optimum production schedule has been obvious for some time, but the methods used to obtain such a schedule have not been so obvious. The current practice is to do a trial and error analysis by hand. In an attempt to improve the way production scheduling is currently done, a new computer based production scheduling algorithm was developed. This paper describes the fundamentals of this newly developed heuristic scheduling algorithm and its application to a gold deposit. The results of this case study show that the schedules, based on the new method, provide improved cash flows compared to production schedules done manually.

Jan 1, 1992

By K. V. K. Prasad

Stochastic simulation has been routinely used for performing risk and sensitivity analyses in a variety of fields. The commonly used means of generating the simulations has been the Monte Carlo approach, which usually employs a Simple Random Sampling (SRS) scheme of the variable distributions. This method is prone to sample clustering and requires a large number of samples to represent the distribution faithfully. This can become problematic for simulating complex processes where it is impossible to run an arbitrarily large number of replicate simulations. The Latin Hypercube Sampling (LHS) method uses a stratified sampling approach that assures representation of the input distributions for any given number of samples. In this paper the LHS and SRS approaches are compared, using a petroleum resource estimation example.

Jan 1, 1994

By G. T. Adel

During the past decade, researchers at Virginia Polytechnic Institute and State University have worked to develop a novel flotation process for treating very fine particles. This process, which is now commonly known as [microbubble column flotation] (MCF), has been shown to be very effective in a number of applications related to fine coal processing. These applications include the retrofit of existing preparation plant circuits and the recovery of additional coal fines from refuse streams. In addition, work conducted under the sponsorship of the United States Department of Energy indicates that the MCF process is capable of producing superclean and ultraclean coals from many eastern U.S. coals. This paper describes some of the basic problems associated with fine particle flotation and the design and operational features of the MCF process used to minimize these problems. Also presented are the results of ongoing pilot- and field-testing programs.

Jan 1, 1989

By B. K. Baird, P. C. Satchwell

The application of cutoffs during and after pit optimization is examined for a lower-grade multi-metallic copper deposit. Pit optimization requires calculation of the net revenue associated with each mining block, incorporating parameters such as metal prices, grades and expected recoveries, mining and processing costs, smelting and refining charges, and penalty element and royalty charges. Sensitivity analysis during pit optimization reveals which of these parameters have a significant effect on the total contained resource tonnage and total contained non-discounted revenue in the optimized pit. The cumulative effect of changing several of the more significant parameters is investigated. Application of a copper cutoff grade to a block inside the optimized pit could result in the less than optimal extraction of the resource. A block with copper grade below the applied cutoff could be economic due to the presence of other metals. Conversely, a higher copper grade block may be sub-economic. The relative merits of applying a copper grade cutoff, “equivalent grade” cutoff and dollar value per ton cutoff to blocks inside the optimum pit are discussed.

Jan 1, 1999

By C. P. Mangelsdorf

Introduction During the 13 years since C. C. White introduced the Birmingham roof truss there has been a revolution in permanent roof support technology. While not all of the emerging concepts have their origins in the truss-resin bolting is a prime example - the combinations and permutations of devices presently available to the underground mining industry reflect a well-spring of creative activity. The purpose of this report is to chronicle a number of roof support system that have same physical similarity to the Birmingham truss, and to report on their application. Definitions The application of the tern "truss" to the device developed by White of the Birmingham Bolt Company in 1967 may be derived from the classical technique of stifwood, by the attachment of an underslung, sometimes pretensioned metal strap, rod or cable. If the beam is separated from the reinforcement by a single block or vertical post it is called a "King's Post Truss". If two equally spaced blocks or posts are used it is referred to as "Queen's Post". When the immediate roof of a mine is visualized as a beam, the Birmingham device completes a structure resembling this latter form.

Jan 1, 1982

By Rudolf Greuer, Gerald Jalkanen, Huann-Sheng Chen

A short cut is presented where the average grade above a primary grade cutoff and its associated byproduct grade(s) are estimated by screening the primary and byproduct grades. For the primary variable, choose samples whose grades are above a cutoff of interest. Compute variograms for the subset of the primary variable. Then using this variogram, krige the blocks of interest only using the samples whose grades are above the cutoff. The next step is to screen byproduct grades by choosing byproduct samples whose associated primary grades are above the cutoff of interest. Next compute variograms for this subset of byproduct samples. Then using this variogram, krige the blocks of interest using byproduct sample grades whose associated primary sample grades are above the cutoff of interest. The results are the average grade above a primary cutoff for both the primary and the associated byproduct variables. Using two simulated primary and reference data sets a case study resulted in the screening krigings performing better than the indicator kriging approach in the first case study. A second case study had mixed results with the primary indicator approach performing better than the primary screened approach. The byproduct screened approach performed better than the byproduct indicator approach.

Jan 1, 2002

By Steven A. Bradbury

INTRODUCTION Passive dust control systems are quickly gaining acceptance in the bulk solids handling industries. The number of applications is increasing due to proven performance, especially in US power plants burning Powder River Basin coal. Air Control Sciences ®, Inc., of Boulder, Colorado, has over forty (40) patented Dustless Transfer ® systems in operation. All of the installations control workspace dust levels to less than 2.0 mg/m3, and in some applications reduced conveyor dusting by over ninety-eight percent (98%). Passive systems control fugitive dust emissions by minimizing the induced airflow in bulk material transfer and slowing its velocity. Traditionally, fugitive dust control in the mining industry was accomplished using either dust collection systems or dust suppression systems. The term passive dust control, indicates these methods don't use any active dust collection or suppression. Passive dust control systems are best suited to transfer from one conveyor to another. They can also be applied to transfers from feeder to conveyors.

Jan 1, 2004