Search Documents

By James L. Parks

This paper describes improvements in SAG and AG mill liner designs and their cumulative effect on wear life and mill availability. Routine procedures used by many SAG and AG mill operators to improve liner life are reviewed. Guidelines are provided for estimating the time required to replace worn liners along with practical methods to reduce downtime for liner replacement. Finally, the effects of mill operating conditions on liner wear life and breakage are considered.

Jan 1, 1998

By J. Kemeny, B. Norton, T. W. BoBo

Digital image analysis systems to quantify particle size of crushed materials have successfully been applied in large-scale mining operations throughout the world. Particle size measurement at various crushing and sieving stages, especially in aggregate production, will facilitate the industry’s desire and need to achieve higher levels of process control and automation. This paper will 1) summarize applications of digital image analysis in the industrial minerals industries and introduce the Split-Online technology; 2) detail an actual recent test application of digital image analysis that ultimately lead to the installation of an automatic, non-invasive particle size distribution monitoring system; 3) document how this information is being applied: and 4) summarize the new Split-Online Aggregates Module now available.

Jan 1, 2004

By S. Gupta

Froth flotation is a process commonly employed for the selective separation of phosphate from unwanted mineral. Column flotation has become widely accepted in the mineral processing industry, including phosphate industries, due to its ability to improve selectivity, lower operating cost, lower capital cost, and superior control. In this work, a hybrid model is developed that combines a physicochemical model with artificial neural networks. The physicochemical model is based on axial dispersion with first order collection rates. A new approach, in which both frankolite (the desired mineral containing phosphate) and gangue (undesired product) are modeled, enables prediction of grade of the recovered product. Thus, two basic parameters are required in this model: flotation rate constants for frankolite and gangue. Artificial neural networks are used to predict flotation rate constants. The model also takes into account the particle size distribution and predicts grade and recovery for each particle size range. The model then combines grade and recovery for each particle size range to determine the overall grade and recovery of the column. The model is validated against laboratory column data.

Jan 1, 1998

By J. C. Agarwal

A significant portion of the, coal mined by U. S. Steel is beneficiated to upgrade the quality of the resultant coke to meet blast-furnace requirements. Primarily because of degradation from modern mechanized mining methods, a considerable quantity of the coal to be beneficiated is in the 1/4-inch by 100-mesh size range. In the cleaning plants, this coal is usually cleaned on concentrating tables and then mechanically dewatered in solid-bowl centrifuges to 9 to 14 percent water. At some plants, to further decrease the amount of water shipped with coal, and to improve the coking characteristics of the coal at its destination, mechanical dewatering is followed by thermal drying. At U. S. Steel's-Alpheus preparation plant at Gary, West Virginia, approximately 50 percent of the total coal produced is in this fine size range, and two fluidized-bed dryers are used for the thermal drying step. The two fluidized-bed dryers are 14 feet in diameter and were designed by the Dorr-Oliver Company. Although the original design called for a rate of drying equivalent to 37 tons, of moisture per hour, presently they are removing twice that amount. This paper describes, the major problems encountered' in operating these dryers at the present, high capacities and how they were overcome.

Jan 1, 1963

By K. T. Cunningham

The Oakfield, New York Hine of the United States Gypsum Company is a shallow, room and pillar mine developed in the Camillus Formation of Silurian Age on the up-dip edge of the northern Appalachian Basin. The gypsum comes to subcrop beneath a variety of glacial materials and is subject to solution activity by groundwater. A geologic environment unfavorable to mining activity is thus created. Since 1978 seismic studies have been used to supplement core drilling to determine a conservative boundary between normal and questionable mining environments. A single channel seismograph, originally in use, is now replaced by a twelve-channel unit and is used to determine bulk material velocity which is the basis for defining the mining limit.

Jan 1, 1987

By Richard L. Ranich, Frank F. Aplan, J. B. Hiskey, Robert S. Thompson, B. J. Scheiner

Acidic waters typified by acid mine drainage, copper dump leach solutions and steel pickle liquors will typically contain SO4-2 and cations such as Fe+3, AI+3 and for the pickle liquors, sometimes Cr+3. These acidic waters will often react with limestone, present naturally or introduced for purposes of solution neutralization, to form reaction - inhibiting coatings of gypsum and gelatinous, metal hydroxide precipi¬tates. The coating thickness, as a function of pH, was quantified for both reactive (calcite, limestone) and non-reactive (quartz, barite, fluorite) minerals, and the data were related to the hydroxy species diagrams and to solution turbidity measurements. Coatings were found on the reactive minerals at a lower bulk solution pH than on the non-reactive minerals.

Jan 1, 1993

By Faruk Oksuz, Clay Haynes, David Egger

The United States Army Corps of Engineers (USACE) has committed to solve a major drainage problem in the suburban Chicago community of Griffith, Indiana. The Cady Marsh Ditch is currently undersized and on occasion spills its banks causing flooding and economic setbacks to the community. Preliminary studies have identified both tunnel and surface solutions as being attractive and viable. The USACE has decided that this project is an opportunity to use the design-build contracting approach to maximize ingenuity in project approach and to allow the market to dictate whether a surface or subsurface solution is most attractive. The tunnel would be over one-mile in length through sands, gravels and clay. Water control will be an issue during tunneling. The paper will explore the contracting approach to the project and the adaptation of Underground Technology Research Council (UTRC) guidelines for underground contracting to a design build project. The roles of Owner, Owner’s consultant, and design-build contractor will be defined as interpreted by the USACE and key contract provisions will be described and contrasted with a traditional design-bid-build approach to tunnel construction.

Jan 1, 2003

By M. Manrique, E. E. Vidal, I. Accorsi, P. R. Taylor

Various pyrometallurgical methods for treating ilmenite and zircon concentrates are reviewed. Laboratory experiments using a thermal plasma reactor were performed to evaluate the conversions of ilmenite to TiC or TiC-Fe and zircon to ZrC or ZrC-SiC. Results are examined and possible processing routes are identified.

Jan 1, 1999

By K. H. McDaniel, D. M. Loring

The underground ventilation system at the Waste Isolation Pilot Plant (WIPP) provides for the unparalleled ability to ensure the safety of the workers, the public and the environment. Although small spatially, the system can vary the airflow from 31.2 to 217.1 m3/s (66,000 to 460,000 cfm). The system can automatically incorporate HEPA filtration in the event of radioactive contamination. Remote-capable regulators individually control the four main splits, and they can be adjusted from the surface if necessary. A ventilation remote-monitoring and control system provides real-time information. Future areas of concern include DPM compliance, system psychrometry, logic-based real-time mine-ventilation simulation and automation using PLC technology. This paper discusses the evolution of this system.

Jan 1, 2003

By Robert L. Runkel, Kenneth E. Bencala, Briant A. Kimball, Katherine Walton-Day

The solute-transport model OTIS and the reactive solute-transport model OTEQ were used to simulate geochemical conditions in Cement Creek, a tributary to the Anirnas River in Colorado. OTIS was used to depict instream zinc concentrations, and to simulate the effects of two remediation scenarios on zinc concentrations at the mouth of Cement Creek. These simulations do not account for effects of changing stream pH on metal concentrations. Preliminary simulations using OTEQ to account for instream pH changes were unsuccessful due to the spatial nature of mixing processes, and insufficient information about the thermodynamic properties of precipitates forming in mixing zones.

Jan 1, 2000

By J. M. Scharer, Bruce E. Halbert, Lysane Bouduc, Douglas B. Chambers, Jennifer L. Kirkaldy, Carol M. Pettit

Io contrast to acid mine drainage (AMD), neutral mine drainage (NMD) has not yet received widespread attention. Metal and sulphate concentrations can be elevated and of concern in neutral drainage from waste rock and tailings. In the present paper, metal release in high ionic strength mine drainage at neutral pH is evaluated at several mine sites. Specific factors including oxidation rates, buffering capacity, and hydrology are also addressed and their effect on the production of contaminated NMD from mine wastes is evaluated. Case studies are presented involving current seepage water quality and predictive geochemical modelling to illustrate the possible time frame and magnitude of the contamination.

Jan 1, 2000

By J. K. Mokka, P. D. Rao, H. K. Lin

Extensive exploration has resulted in delineation of a massive sulfide district on the north flank of the east-central Alaska range. The district covers approximately 400 mi2 and contains numerous stratiform, transposed and some replacement type sulfide deposits ranging in size from less than 1 million st to 20 million st. Five types of ores were sampled for the study. Mineralogical analysis revealed that the minerals are too fine grained for conventional grinding and beneficiation. Hydrometallurgical studies were conducted using ferric chloride as a lixiviant. Ore microscopic studies as well as electron microprobe analyses of minerals in the raw samples and leach residues explained the low recoveries for certain elements as well as sources of impurities that need to be eliminated from the process streams.

Jan 1, 1992

By N. D. Cristescu

An analysis of the interaction between a creeping rock and a yieldable lining is presented. The following cases are considered: an elastic lining, a lining made of circular shaft rings that may slide at their joints, a lining made of circular reinforced concrete panels with wooden compressible strips inserted between the longitudinal joints and a yieldable support that has a compressible broken-rock stratum between the support and plane rock. By formulating a mathematical model for the rock-lining interaction, one can optimize the sequence of excavation-lining application. To keep costs to a minimum, one can also choose the most appropriate lining for the corresponding rheological properties of the rock.

Jan 1, 1997

By A. E. Isaacson, T. H. Jeffers

The U.S. Bureau of Mines (USBM) is investigating arsenic removal from dilute waters using a biological precipitation/chemical adsorption system. The method includes (1) inoculating water with ferrous salts to increase hydrogen sulfide generation by indigenous sulfate-reducing bacteria, (2) utilizing the hydrogen sulfide to precipitate the bulk of the arsenic as arsenic sulfide, and (3) using beads containing ferric oxyhydroxide to remove the remaining arsenic. This approach was applied to a contaminated water containing 13 mg/L As. Arsenic extractions up to 99% were achieved. The use of sulfate-reducing bacteria is particularly warranted in this situation since most of the required nutrients are present in the water. Based on successful initial efforts, planning is underway to conduct a pilot-scale test at the site.

Jan 1, 1995

By Robert J. Timko, R. Lincoln Derick

This report presents a Bureau of Mines evaluation which examined the extent of gas leakage from sealed areas in underground coal mines and measured the effectiveness of commonly used structures for controlling the quantity of gas exchange from these areas. Evaluations were performed on five abandoned areas in two operating underground mines within the same coal seam. Methane and oxygen levels inby the seals were monitored to determine if the gas leakage was unidirectional or bidirectional. Results from this and prior work dealing with minimizing gas leakage were then applied to a newly abandoned area. Also discussed are bulkhead site preparation, construction plans, techniques for monitoring the status of the atmosphere within the sealed volume, and a modified European method for controlling gas migration from the sealed volume to the active mine.

Jan 1, 1991

By Edmond Donovan, O&apos

With the increase in complexity of conveyor systems and the inexorable demand for more capacity and availability, the ability of designers to accurately predict performance is becoming increasingly important. Dynamic analysis techniques for modelling wave mechanics in conveyors are finding increased applications. Unfortunately, the reliability of these modelling techniques is dependent on a thorough understanding of the performance characteristics of the components that make up the system. These characteristics include such things as response rate, hysteresis and efficiency. Some parameters such as idler rolling resistance can be easily quantified by measurement. More complicated drive parameters are difficult or impossible to measure, particularly in large horse-power equipment. One method of quantifying or at least bracketing the performance envelope of complicated pieces of equipment is to construct a mathematical model. This can be done quickly and economically, and the influence of various parameters can be determined. This paper sets out to demonstrate by example the usefulness of this technique in gaining an understanding of complicated systems. The model is developed and the influence of a number of variables are examined.

Jan 1, 1996

By W. M. Husslage, M. E. Kock, T. Bakker, R. H. Heerema

Permeability in the blast furnace shaft is adversely affected by low-temperature reduction degradation of sinters. The fundamental cause of this is the expansion of the iron oxide phase resulting from the reduction of hematite to magnetite. The present study shows that expansion behavior during the hematite/magnetite reduction .step and the resulting microstructure are strongly influenced by the reduction temperature (partial oxygen pressure), the reducing agent and the nature of the hematite. The reduction rate is of minor importance. A reduction mechanism is proposed that can explain the dilation behavior and the magnetite microstructure. The results provide better insight into the reduction degradation behavior.

Jan 1, 2000

By R. L. Ziegfeld

It has often seemed to me that people are too prone to turn to new and untried materials in an effort to solve their problems, without giving sufficient consideration to the old stand-bys, except as a last resort, It?s a little like middle-aged men who are swept off their feet by the fresh beauty of a young girl without first considering the many advantages that a more mature woman has to offer. Maybe it?s because, like the older woman, the older materials have to make a determined effort to keep themselves looking young and attractive. T at?s just about the situation with which the lead industry is laced. We have to make a determined effort to keep lead looking young and attractive to industry. However, there is one difference and it is important, Lead can not only be kept looking young, but it can, in fact, actually be kept young, This results from two things. First, industry and technology are constantly changing. For example, we have known for years that the density of lead makes it ideal to stop gamma rays, but it is only recently that atomic fission as a source of gamma radiation has become an important tool of industry, That makes old knowledge about lead useful in developing a new market for it.

Jan 1, 1958

By K. V. K. Prasad

Solution of most engineering problems requires, in addition to vast numerical calculations, substantial use of practical judgement and expertise. With advances in applied mathematics and computer technology, the numerical aspects of problem solution have reached a considerable level of maturity. However, it is only recently that approaches like the expert systems methodology have been developed to incorporate the judgemental aspects as well. For rapid development and prototying of expert systems, expert system building tools or "shells" have become widely available. For the expert system developer, identification of the key characteristics of the problem domain and selection of the right expert system tool are of crucial importance. In this paper, the important attributes required in an expert system shell for use in the development of a mine ventilation planning expert system are discussed. These attributes are general in that most engineering problems in mining would have these requirements. Also, the results of an exercise undertaken to evaluate commercially available shells for application to mining engineering problems are presented.

Jan 1, 1989

By Terry O. Arney

Ore Reserve Models are well established evaluation and mine planning tools. BY definition, these models are made up of regularly sized blocks, arranged in a three dimensional matrix. Two dimensions correspond to north and east directions, and the third, to the depth or elevation. The dimensions of the blocks need not be equal, but generally at least two of the dimensions are equal. The blocks are located in space by coordinates which are generally translated into index values for computer applications. Each block will have quantitative attributes, such as grades, densities, rock characteristics, etc. assigned to it. The process of assigning values to each block in the three dimensional matrix is the process of ore reserve model development. One of several interpolation procedures may be employed to predict the value of a block, based on surrounding data. Block value models have several uses. The utilization of block models in ore reserve computations is quite common. Here, ore reserves may be calculated by level or by cross-section for the entire deposit. For each ore reserve calculation, multiple cut-off grades may be analyzed to determine the ore reserves under different cut-off conditions. The other major use of block value models is in mine simulation. Through simulation, profitable studies that analyze the effect of alternate ore removal sequences can be undertaken to determine economic optimality. Other studies that are undertaken in mine simulation problems include the evaluation of mine layout, pit slope effects, and the impact of varying cut-off grades.

Jan 1, 1974