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By C. L. Lin

A PC image-based, on-line instrument for the measurement of coarse particle size on a conveyor belt is under development. Both the hardware and software required to implement such a system are discussed, including the interface for the special image acquisition hardware. The system concept is given with examples to illustrate the step-by-step procedure for the implementation of image-processing algorithms.

Jan 1, 1992

By Kelly J. Driscoll

Impure zinc (98.5%) was electrorefined to high purity zinc (99.995%) using a fused salt electrolyte of molar composition 1: 1 : 1 :2 ZnCI2:KCl:NaCl:LiCl with a current efficiency of about 90% at 723 K. A recessed channel electrorefining cell was developed which achieved excellent mixing of both the metal and the electrolyte and by ensuring a very small anode to cathode spacing the voltage drop across the cell was 0.16 V and at a current density of 7kA m-2. The physical characteristics of the cell were observed using a low temperature model which showed the formation of droplets and rivulets which provided mixing. The application of this approach to the refining of other non-ferrous metals is discussed.

Jan 1, 1992

By K. V. K. Prasad

Forecasting mined grade variability from exploration information is a challenging task in mine planning. For effective planning of activities such as workplace scheduling, ore grade quality control etc. development of realistic numerical/simulation models of in-situ variability from exploration information is an essential first step. Geostatistical conditional simulation (GCS) is one of the well known methods to develop these simulations. Recently, stochastic fractal models based on the assumptions of scale-in variance and self-similarity have been used for developing simulations of several natural phenomena. It has been suggested that these models might permit generation of short-scale variability information from exploration data with greater fidelity when the data satisfies the attendant assumptions. In this paper the stochastic fractal models are reviewed and their relationship to geostatistical variogram models is examined. A comparison of the two simulation techniques has been per-formed using coal sulfur data from a mined out coal property. The results of this comparative analysis are also presented in the paper.

Jan 1, 1992

By J. Alton Burks, Roy C. Bartholomae

The chain conveyor is utilized extensively in underground mining to convey raw ore, especially coal. It is estimated that several thousand loading and continuous mining machines rely on this type of conveyance. Although the chain conveyor is both efficient and highly reliable, its use is generally associated with the production of noise levels that often exceed 105 dBA at the operator's position. Thus, it is one of the most significant contributors to the occupational noise problem experienced by miners in the underground coal mining environment. Conventional engineering noise controls that result in an average reduction of 4 dBA have been previously designed and implemented. However, a novel solution involving a change in conveyor operation has been proposed that takes advantage of two aspects of conveyor noise: 1) conveyor noise has an approximately cubic dependence on conveyor chain speed and 2) due to the damping provided by coal, a full conveyor is 5 dBA quieter than an empty one. An engineering analysis has shown that a significant reduction in the operating noise level of a typical continuous miner can be achieved through the use of an adjustable speed drive automatically controlled by a coal loading sensor that maintains a full conveyor at all times. The potential reduction depends primarily on the mining conditions (coal seam thickness and the presence of either rock or water) and varies from 7-18 dBA. Other benefits to be derived from the use of a variable speed drive include reductions in power consumption, dust, and maintenance costs.

Jan 1, 1992

By Qixiang Y

The strength of coal mass saturated with gas is an essential parameter in studying the mechanism of gas and coal outburst,and its prediction method. Up to now, there has not been a method for determining the strength of coal mass saturated with gas.This paper describes a new method whereby the strength of in-situ coal mass can be determined and stored continuously and automatically. The simulation results obtained in the laboratory indicate that the new method allows a fast, reliable, inexpensive and convenient determination of the strength of coal mass.

Jan 1, 1992

By D. Shink

A small scale continuous flotation cell was designed and constructed at Noranda Technology Centre to develop a mobile testing flotation circuit located next to the production circuit. This mobile small scale flotation pilot plant can easily and economically be set up at any circuit in a mill and used to evaluate and predict plant performance against a given flotation condition. The main feature of the cell, beside the provisions of automatic pulp level and feed rate control, is to provide a reduced surface to volume ratio approaching to that of an industrial machine. This paper describes the basic design and the results of various testwork carried out to date including aeration, conditioning, reagents, recirculation, flotation gas, etc. are presented in comparison with the plant production results.

Jan 1, 1992

Maintaining and improving the economics of open pit mining in the future requires understanding of the characteristics of open pit mining that are different to other mining or business activities, designing mines in the first place to be less susceptible to changes in these important characteristics, and adopting strategies which yield reliable returns despite unforeseen change. Planning and production personnel require guidelines and performance standards that are based on sound economics not solely on production criteria. The guidelines adopted for long-term implementation must assume a declining price for mineral products along with declining real costs, with research efforts directed at development of both evolutionary and revolutionary ideas aimed at implementation. Decision-making must focus on risk and probability criteria rather than just simple return-on-investment criteria, and the approach for management of personnel must support the higher level of communication essential for fast decision-making in the new environment of continual change.

Jan 1, 1992

By S LeClair

Intelligent manufacturing involves intelligent, product-directed systems that facilitate the on-line, real-time generation of an improving product process cycle. A first step in the journey relates to self-directed systems which have the ability to reason and create their own processing paths in response to varying product and process conditions encountered during the process. This paper discusses an application of self-directed process control in the manufacture of graphite-epoxy laminated composites. An Air Force team involving researchers and production personnel have caused the development of a system now in use at the Air Force Logistic Center at McClellan Air Force Base in Sacramento CA. The paper discusses results and lessons learned in the process of trying to speed the implementation of research efforts which show significant potential of improving the product quality in less time and at less cost

Jan 1, 1992

By Thomas M. Barczak

This U.S. Bureau of Mines report chronicles the historical development of longwall mining in the United States and speculates on future developments to the turn of the century. The involvement and contributions made by the Bureau during these developments are also discussed. Two major periods of history are analyzed: (1) from 1875 to 1950 when small advancing faces were operated manually, and (2) from 1950 to 1990 when mechanized extraction and powered roof supports provided a system to efficiently extract large coal panels. Five eras of technological development during the modern period are described and analyzed. These eras discuss the development of (1) mechanized extraction, (2) powered roof supports, (3) high-capacity roof supports, (4) shield supports, and (5) system automation. Current trends are analyzed in terms of longwall utilization, face production, support capacity, face widths, and new technological developments. From these analyses, the future of longwall mining to the year 2000 is speculated. It is concluded that longwall mining will continue to grow in importance during the next decade and that the next major technological milestone will be the realization of a fully automated longwall mining system.

Jan 1, 1992

By G. A. Davidson, P. G. Williams

"New developments in centrifugal slurry pump technology are discussed in relation to their importance for improving pump operation and reliability.Experimental data obtained by measuring the velocity of liquid flows in a slurry pump casing using Laser Doppler Velocimetry are presented. This demonstrates the importance of selecting pumps with the proper hydraulic design to provide optimum efficiency, maximum part life and minimum operating cost.The paper also discusses the use of new wear resistant materials, such as ceramic/metal composites, which can significantly improve the life of parts exposed to abrasive media. The results of laboratory attrition tests are presented. IntroductionCentrifugal slurry pumps are of primary importance for the hydro transport of abrasive and corrosive media in the mineral processing industry. As for all process equipment, slurry pumps must be carefully selected and operated to provide optimal performance. To achieve this, it is necessary to select equipment which will provide efficient and reliable operation for the specific service conditions and incorporates the best materials available to obtain maximum parts life.Abrasive wear of liquid end components is the most important aspect that distinguishes the design and application of slurry pumps from other types of pumps. It is therefore necessary to have a fundamental understanding of the mechanical interaction between pump components and the media being handled, as this will impact significantly on hydraulic design, mechanical reliability and selection of wear resistant materials. Recent advances in computational approaches'» have greatly improved the prediction of wear rates in pump casings by facilitating the solution of complex equations which describe the wear mechanisms mathematically. In conjunction with this, new experimental techniques allow researchers to measure flow fields in pump casings using non-invasive devices such as Laser Doppler velocimeters."

Jan 1, 1992

By A. J. Paul

Traditionally, 16"/50 caliber projectile shells have been fabricated from forged steel. The Naval Surface Warfare Center (NAVSWC) has determined that cost savings of approximately 60% (-$4.7M/year) as well as improved shell fragmentation can be achieved by casting these shells from austempered ductile iron. One of the technical concerns arising out of this material substitution is the role of the casting process in controlling the quality of the cast shells. Optimizing the process through proper orientation of the mold, placement of chills, superheat, etc., can minimize shrinkage porosity and, consequently, flaw size. For this purpose, the mold filling and subsequent solidification of the projectiles was simulated using a 3-D, fully transient, coupled fluid flow and heat transfer model based on finite differences. Several casting orientations were investigated and the casting parameters were varied to optimize the process and minimize casting defects. A comprehensive software tool, which was developed using state-of- the-art visualization techniques, has been used to analyze the process of casting. Emphasis is placed on the use of this visualization tool as an aid to the foundry engineer for process optimization.

Jan 1, 1992

By J. E. Chilton

Methanometers with catalytic heat- of-combustion sensors used in coal mines today will read low for flammable gases when oxygen (0,) concentrations are low or when methane (CH,) concentrations are greater than 10%. Thus, these methanometers may not be reliable during operations such as fire fighting or recovery of sealed mines. The U.S. Bureau of Mines developed a total flammable gas detector (TFGD) to measure CH, at concentrations up to 100% and to measure flammable gases in low 0, concentrations. This paper describes the operation and construction of the TFGD and discusses measurements of flammable mine gases obtained from a mine in western Pennsylvania.

Jan 1, 1992

By J. Diao

In order to understand the flotation kinetic behavior of coal and associated mineral matter, a detailed investigation was conducted in a 2-liter Denver flotation cell using three high sulfur coals at three feed sizes, minus 28. 100 and 200 mesh. Subsequently. the flotation products were sieved into different size fractions and analyzed for their ash and pyritic sulfur content in order to delineate the effect of particle size on the rate at which each constituent floats. The results were tested with several different flotation kinetic models and the best model for coal was then chosen. The flotation rate constant and the ultimate recovery calculated from a kinetic model were used to delineate the effect of particle size, collector (dodecane) and frother (MIBC) dosages on the flotation kinetics of coal, ash and pyrite.

Jan 1, 1992

By John L. Hostetler

GALFAN, the Zn-5% Al-mischmetal hot-dip galvanizing alloy is coated onto steel sheet, wire, and tube using high-speed continuous galvanizing lines. Factors critical to producing high quality GALFAN are reviewed, The relationship between minimum mischmetal content in the GALFAN alloy and furnace dewpoint will be described. The relationship between peak annealing temperature and furnace dewpoint will also be shown. Typical suategies for operating multi-purpose hot-dip galvanizing lines including GALFAN will be described. A recent development has allowed preparation of steel smp for GALFAN coating using aqueous fluxes rather than high temperature annealing. This allows production of GALFAN-coated smp without over-ageing of the steel, and allows high steel strengths and hardnesses to be obtained. The principles of this process will be described.

Jan 1, 1992

By Y. S. Roditis

A new method for interpolating a block model is proposed, where both the diamond drill holes (DHs) and blast holes (BHs) data are used. Combining these data types poses a geostatistical "class size" problem due to the different statistical properties of the densely populated BHs and the sparsely populated DH data. This paper discusses how linear regression was used to adjust the DH values prior to the interpolation to account for the "class size" problem which is inherent to the procedure. The correlation between the BHs and the DHs is found. The DHs are then corrected based on the regression line. Each block that falls within a certain range of influence of a blast hole is assigned a different code and is interpolated with the combined BH and regressed DH data set. Blocks that fall outside the range of blast hole influence are interpolated using the original DH data set. A comparison against other methods, indicate a 12% improvement over using DHs only and a 2% improvement over using BHs only.

Jan 1, 1992

By Walter G. Steblez

The countries of Eastern Europe are former members of the Council for Mutual Economic Assistance (CMEA). Geographically, they are located in Central Europe (Poland, Hungary, Czechoslovakia) and Southeastern Europe, largely in the Balkans (Yugoslavia*, Bulgaria, Romania and Albania*). It is important to remember that all of the countries of Eastern Europe had central planning imposed on them by the Soviet Union during the years following World War II. "Stalinist" policy for industrial development had three important tenets: • central economic planning, or a nonmarket-based command economy with administratively set prices; • economic priorities that stressed the development of heavy industries such as mining, metallurgy (steel) and heavy machine building; and • self-sufficiency at all costs, which was aimed at abolishing reliance on the world capitalist market, or reducing it to a minimum. Essentially, the system of industrialization that was used in the Soviet Union in the 1930s and 1940s was imposed on Eastern Europe. Organic market economic development in Eastern Europe ceased during this period. The flaws of this experiment became apparent when mineral processing facilities were set up in many areas of Eastern Europe that did not have reliable resources. Poland, Hungary and Romania are good examples of this situation. The Soviet Union became the principal supplier of iron ore and other minerals and mineral fuels, not only to these countries but to the Bloc as a whole.

Jan 1, 1992

By J. Mark Richardson

Steady-state flowsheet simulators for mineral processing plants have evolved to a current high level of utility and accuracy. Reliable, general-purpose, semi-empirical models now exist in nearly all unit operations categories particularly in the areas of comminution and classification. .These models, installed as user-selectable functions within the integrated frame- work of flowsheet balance-solver software systems, can be strung together to represent any plant configuration. In addition, CAD-like graphics, data reconciliation and model parameterization functions have become standard features of the current generation of integrated plant simulators. These advances have given engineers the capability to investigate many different plant scenarios while requiring a minimum of actual plant testwork. This paper describes a methodology and an integrated software package which are being successfully applied in a number of operating plants worldwide to predict plant performance under changing conditions. Those conditions which can be changed include effect-of ore type, feed size, water addition rates, equipment geometries and flowsheet modifications. By using data from actual plant optimization exercises in real mills, the paper illustrates and out- lines a technique which includes plant data collection, ore breakage testing, flowsheet simulation, model-fitting (parameterization), data adjustment and model experimentation. Brief descriptions of some unit operations models, such as autogenous mills and cyclones, are provided as examples of the current state of such models. Ore breakage testing and its relation to certain models is also discussed. Computer- generated size-distribution graphs, along with tabular data generated by the simulator, round out the presentation and serve to demonstrate the real- ism and accuracy of the models. The paper concludes with a partial list of cases where this technology has been successfully applied.

Jan 1, 1992

By E. D. Sehnke

The refractory materials industry provides the largest commercial market for nonmetallurgical grade bauxite. Refractory grade bauxite is prepared from bauxites having low iron, titania, and alkali content by calcining at temperatures near 1,650° C. Although there are substantial bauxite reserves in the world, premium grade bauxite ores suitable for use in refractory applications are limited to only a few specific sources, primarily in Guyana and the People's Republic of China. Consumption of bauxite for refractory use is closely associated with the production and consumption of primary metals, in particular iron and steel. Barring major disruptions within the principal producer nations, sufficient supplies of refractory bauxite will be available to meet world demand well into the next century, and raw material costs will continue to determine the availability of markets for bauxite-based refractory products.

Jan 1, 1992

By G. L. Mowrey

One critical element of the US Bureau of Mimes computer- assisted mining research program is the development of a reliable coal interface detection (CID) system. Several promising CID concepts currently being investigated by the Bureau include natural gamma radiation (NGR), vibration and passive infrared. To help establish which CID sensor technologies need to be developed for a given seam, coal and adjacent rock samples (immediate roof and floor) are being collected from selected major coal seams in the US and are being analyzed in terms of NGR and other geophysical measurements. This paper provides a brief overview of the Bureau's work in these CID areas.

Jan 1, 1992

By Daryl R. Tweeton

The Bureau of Mines has developed PC-based tomographic computer programs for geophysical applications, and is making them available to potential users as part of a Bureau plan to facilitate the transfer of technology to industry. These programs were initially developed for predicting and monitoring the flow pattern of leach solution during in situ mining. Seismic crosshole tomography has located fractured zones of low seismic velocity and saturated zones of high seismic velocit above the natural water table. The Bureau has applied tomography also to assessing high-wall blast damage, and examining the integrity of mine-related geological structures. The tomographic programs include the straight ray pro ram BOMTOM (Bureau of Mines Tomography? and the program BOMCRATR (Bureau of Mines Curved Ray Tomographic Reconstruction) that can be run with either curved or straight rays. Both programs provide optional mathematical constraints to help counteract the nonuniqueness of reconstructions that occurs with crosshole data. They are available from the Bureau free of charge. With typical data sets, they can be run on a 386 microcomputer with 640 Kb RAM. BOMTOM was described in the Bureau Report of Investigations 9159, so this report emphasizes BOMCRATR. Curved and straight ray reconstructions using seismic field data collected while simulating injection of leach solution were compared. The curved and straight ray tomograms were quite similar even with velocity variations of more than 50 percent.

Jan 1, 1992