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By R. L. Grayson

Compliance standards for respirable dust, which are reduced because of high quartz concentrations, have become an industry-wide problem. Research on the physical and chemical character of quartz-classified particles in respirable coalmine dusts indicates that they mine exist in intermixed layers or may be coated by clay or coal material. The relative amount of intermixing varies with the coal seam being mined. If most of the quartz particles of a mine dust are "pure," then the dust may have a high fibrogenic risk potential because of truly free silica and the compliance standard should be lowered. If, however, the quartz is locked inside another material matrix or coated, a reduced compliance standard may not be appropriate.

Jan 1, 1992

By S. Chunhui, W. Anbin, R. B. Cook

The Xicheng is one of China's largest lead-zinc (Pb-Zn) districts with known minable reserves in excess of 10 Mt (11 million st). The centrally located Changba-Lijiagou and nearby deposits are representative of the district. They consist of stratiform and stratabound zones of pyrite-sphalerite-galena mineralization within deformed, moderately metamorphosed Middle Devonian clastic and carbonate units. When considered with other similar districts that extend for several hundred kilometers to the east, a major episode of Devonian sedimentary exhalative mineralization is indicated.

Jan 1, 1992

By C. J. Pritchard, A. B. Cecala

An evaluation was performed on a district recirculation system at a trona mine in Granger, WY. A 1.52 m-diam (5 ft-diam), 37.3-kW (50-hp) vane axial fan was installed in a crosscut between the intake and return airways and recirculated about 31.4 m3/s (66,578 cfm) of air back into the intake. This amounted to a recirculation factor of about 20% of the return air. This air was part of the primary ventilation to three different continuous miner sections at operating distances of between 610 m (2000 ft) and 1829,m (6000 ft) from the recirculation fan. The mine environment was constantly monitored for respirable dust, methane and carbon monoxide in the operating sections and in the main intake and return entries. In addition, air samples were taken with and without the recirculation system during the evaluation and analyzed using gas chromatography. The results of this study showed only small increases in dust, while all other mine contaminants remained at such low levels that it was impossible to determine any relative changes from the recirculation system. Because of this, a brief SF6 tracer gas analysis study was subsequently performed to more precisely determine an increase in a mine contaminant with the recirculation system.

Jan 1, 1992

By V. Ciribeni, R. J. Ferretti, C. de Arrieta, E. E. Rossi

The relationship between collector concentration and the solution pH at which flotation occurs is discussed for different minerals. When flotation results are plotted as log of the concentration against pH, the values define areas of total, partial or no flotation. The experiments were performed in three different conditions: a) floating with the same solution used for conditioning; b) floating with water at the same pH as the conditioning solution; and c) floating with water at pH = 7. In each case, the results obtained are quite different. It is suggested that the presence of a second layer of collector reduces flotation over some domains in the graphs. These domains are called depression areas.

Jan 1, 1992

By Ernest Y. Baafi

The usual tasks performed by a mine store include .removal, replenishment, ordering and deletion of items and updating of stocks. A personal computer Mine Store Inventory Database System MIDSYS for monitoring stocks in such a store is presented. The system consists of series of relational databases developed in dBASE III+ environment. The system has three main modules comprising of a store management module, a display module and an employee-store operation module. The third module is useful in tracing movement of store goods. The MIDSYS is menu .driven with help functions at all levels.

Jan 1, 1992

By Fernando de Oliveira Durão

A complete computer package for the steady-state simulation, either in analysis or in design mode, of mineral processing flowsheets is described. The main features of the simulation package are: modular architecture, flexible structure and sequential solution strategy. Different detail levels of mathematical models of several mineral processing unit operations have been developed and implemented as unit modules (FORTRAN routines). Unit operations currently modelled are: coarse/fine crushing, grinding, screening, hydrocyclone classification, gravity separation, heavy media separation, froth flotation, high gradient magnetic separation and solid-liquid separation. In design mode, a simulation study is stated as a general non linear optimization problem. The objective function is a weighted sum of square deviations between the design specification set points and the calculated values, subject to non linear equality and inequality constraints. The optimization problem solution is obtained solving successive Quadratic Programming subproblems followed by inexact line search of an exact penalty function (Powell algorithm). One non trivial example is discussed, illustrating the design capabilities of the simulation package.

Jan 1, 1992

By Daniel R. Stewart, Ralph R. Sacrison

The function of the geological engineer is to assist in mine planning and operations by collecting, interpreting, and applying geologic data to the solution of engineering problems. The geologist supports this effort by collecting additional geologic information specifically useful to the engineer. This use of geologic information reinforces the value of mine geology to the mining process beyond the traditional role of orebody definition. Work discussed includes: evaluation of caving strategies at the Climax and Henderson mines, support definition and slope stability at the Climax mine, and some uses of geology in cavability estimation for the Mount Emmons project.

Jan 1, 1992

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 T. Leftwich, G. Faison, K. Pavlich, R. Borden, S. Pavlou

Recent regulatory and policy initiatives under the Resource Conservation and Recovery Act (RCRA), and the Comprehensive Environmental Response Compensation and Liability Act (CERCLA), will have a significant effect in risk reduction requirements for the mining and minerals processing industry. For example, Congress is considering regulating 20 special wastes from the processing of ore and minerals through RCRA Subtitle D and TSCA. The performance of risk analyses and environmental planning at mining projects is often driven by Federal and state regulatory standards. Recent regulatory and policy initiatives by the Environmental Protection Agency under the Resource Conservation and Recovery Act (RCRA), and the Comprehensive Environmental Response Compensation and Liability Act (CERCLA), will have a significant effect on environmental planning and risk reduction programs for mining and minerals processing. Regulatory programs implemented under other Federal laws including the Safe Drinking Water Act, Clean Water Act, and Clean Air Act will also impact industry practices. This paper provides: 1) a brief overview of mining waste and mining waste management, and 2) a description of these regulatory initiatives and a discussion on the impacts of new requirements on environmental and risk reduction programs in the mining industry.

Jan 1, 1992

By R. A. Wharton, Z. Yang, R. W. Smith

The electrokinetic and flotation behavior of the green alga Chlorella vulgaris was studied in the absence and presence of Pb(II), Al(III) and flotation collectors. It was found that the presence of Al(III) is necessary for good flotation of the organism, whether or not Pb(II) is present, when dodecylammonium chloride or sodium dodecylsulfate is used as collector. Best flotation using dodecylamine is at about pH 8, and best flotation when using sodium dodecylsulfate is at about pH 4. It appears because of the small size of the organisms that the Al(III) is necessary for flocculation to enhance bubble-cell contact and C. vulgaris removal from water. When N-dodecyl-2-aminopropionic acid is used as collector, good flotation occurs at about pH 4 without the addition of Al(III).

Jan 1, 1992

By B. J. Arnold

A coal's size distribution clay content and moisture content can affect its handling behavior. But the combined effects of these properties and the effects of other properties are not known. Research underway at CQ Inc.'s (formerly EPRI's) Coal Quality Development Center (CQDC) and at Iowa State University (ISU) will answer these questions as part of a four year project to develop a coal handleability index for utilities to use when specifying coals. This paper will present preliminary data from the first year of the project, which focused on obtaining data on the chemical and physical properties of carious coals and their measured handling properties. Additionally, size, ash and moisture analyses and shear test data for several coals used at one power plant will be presented along with correlations between these physical and chemical properties and the measured handling properties. These data lead to the conclusion that while moisture content is the most important variable, the amount of -44 µm (-325 mesh) coal fines is a significant factor in determining coal handling behavior.

Jan 1, 1992

By M. C. Roberts

The material composition of product is defined as the quantity of metal used per unit of product manufactured during a year. The material composition of product has shown steady and persistent declines over time for most metals and materials. This tendency demonstrates the continued improvements in manufacturing technology resulting from substitutions of other materials and increases in production efficiency. The purpose of this paper is to use the material composition of product to show the impact of advanced materials on the use of traditional metals.

Jan 1, 1992

By W. L. Cornell, F. W. Benn

The U.S. Bureau of Mines investigated froth flotation techniques to remove heavy metals (Pb, Cu, and Zn) from southeast Missouri lead mill tailings. It has been estimated that southeast Missouri contains between 200 and 300 million st of Pb tailings stored above ground. The tailings were classified as two distinct types: (1) pre- 1968 tailings from the Old Lead Belt (some more than 100 years old) and (2) post-1968 tailings from the New Lead Belt. The objectives of the investigation were to reduce the Pb remaining in the tailings to (500 ppm (<0.05% Pb) and to attempt to recover a marketable concentrate to offset a portion of the remediation costs. The remaining dolomite-limestone would then be used as mining backfill or agricultural limestone. Bench- scale froth flotation removed, in percent, 95 Pb, 84 Cu, and 54 Zn, leaving 94% of the original weight containing, in parts per million, 400 Pb, 40 Cu, and 300 Zn from the Old Lead Belt tailings. Separate flotation tests also removed, in percent, 85 Pb, 84 Cu, and 80 Zn, leaving 75% of the original weight containing, in parts per million, 400 Pb, 200 Cu, and 500 Zn from the New Lead Belt tailings . Concentrates recovered from the Old Lead Belt were retreated to produce a final Pb concentrate containing 72% Pb with a cleaner flotation recovery of 79%. Froth flotation proved to be a viable method to remove the heavy metals.

Jan 1, 1992

By Dr. George W. Annadale, Dr. Adrian G. Chantler

Materials which are likely to produce Acid Rock Drainage (ARV) can be identified with a reasonable degree of certainty. However, it is not currently possible to predict the concentrations of future contaminant discharges with similar confidence. One way of overcoming this problem is to model the uncertainty in knowledge related to estimates of future contaminant concentrations, and utilize this information in a decision model to decide on acceptable levels of expenditure on ARV control measures. The paper presents a risk modeling approach and proposes a decision model.

Jan 1, 1992

By T. N. Moore, E. M. De Souza

Vibratory hand-tools can produce Hand Arm Vibration (HAV) Syndrome in their operators. This disease, often called Vibration White Finger, can cause varying levels of hand-arm discomfort and, in severe cases, impairment. In addition to the human suffering, there are also significant economic repercussions for industry. These include reduced operator efficiency, lost time through increased absenteeism and increasing compensation awards. In the mining industry, jackleg rock drills are a particularly troublesome source of hand vibration exposure. As a result, a significant amount of work has focused on redesigning rock drill handles to minimize hand-transmitted vibration. This paper details the results of a study undertaken to determine the effectiveness of using elastomer covered ("cushioned") handles in place of the standard steel design. The results indicate that, for a particular cushioned design, the overall acceleration level experienced at the hand-handle interface can be reduced by as much as a factor of three, relative to the steel handle. It is also shown that this reduction takes place predominantly in the frequency range above 500 Hz, with performance improving with increasing frequency. Qualitative evaluation of the cushioned handles by the drill operator indicates a significant increase in comfort over the standard steel handle.

Jan 1, 1992

The amount of hydrophobic materials constituting the mineral froth strongly influences the froth viscosity. Higher froth viscosity on the other hand can retard the drainage of physically carried over hydrophobic particles. In phosphate flotation tests a direct correlation was observed between froth viscosity and recovery and an inverse correlation between froth viscosity and grade. Phosphate flotation tests in the presence of a silica depressant indicated that higher froth viscosity is an effect rather than a cause of silica particles reporting in the froth.

Jan 1, 1992

By G. J. Hodges

The Stillwater Mining Company, a partnership of Pittsburg & Midway Coal Mining Co. and Manville Corporation, operates a precious metals smelter at Columbus, Montana to further up-grade concentrates from its platinum/palladium mine. The smelter began operation in the summer of 1990. The gas cleaning system in the facility utilizes "oxidation/dilute mode" dual-alkali scrubbing technology to capture sulfur oxide gases from the process gas streams. This paper describes the rationale for selecting the dilute mode dual-alkali system and summarizes design parameters. Start-up problems and their solutions are also discussed.

Jan 1, 1992

By M. Polat

A combined heavy medium-flotation process which incorporates the advantages of two widely employed cleaning methods, namely, heavy medium separation and flotation was used to achieve improved separation of coal from ash at fine sizes and to recover the heavy medium as a substantially recyclable product. The investigation was carried out in two successive phases. In the first phase, tests were performed to deter-mine the effect of different variables such as the medium density, flotation time, magnetite type, etc. on the efficiency of the process using in-plant samples from Homer City Coal Preparation Plant. In the second phase, the optimum conditions determined in the first phase were employed to determine the applicability of the process to a few Central Pennsylvania coals. It was observed that the process was very effective in recovering the magnetite. In most of the cases investigated, the magnetite was separated from the non-magnetic material at approximate-1 to 99 % recovery with a grade ranging from 95 to 99 %. The grade of magnetite decreased with increase in ash content of coal and with decrease in size of magnetite.

Jan 1, 1992

By S. B. Bhagwat

The United States has abundant coal resources that could last at least another century. and probably longer at present consumption rates. Geographically, the coal resources are distributed over the entire nation including Alaska, although there are no coal deposits in the highly populated areas on the two coasts. This allows free access to the coal, but makes transportation more expensive. Not all coals can be utilized equally because they differ vastly in quality. The sulfur content of coals, considered as the most detrimental acid rain-causing element, varies from as low as 0.3 percent in some areas of the western U.S. to 5 percent or more in parts of the Midwest. The chlorine content, which causes corrosion of plant hardware, also varies regionally. The 1990 amendments of the Clean Air Act of 1963 (CAA) require that emissions of sulfur be restricted and rolled back in two stages by the year 2000. There have been a number of reports expressing concern about the future of the industry in the states where high sulfur coal is produced. The remedies devised by the federal government and many coal-producing states in the past to "se-cure" the future of the regional coal industries have focused on the physical task of removing sulfur rather than the economic challenge of doing so at a cost that will enable high-sulfur coals to survive and compete. The past remedies, generally, were not specific enough to account for the characteristics of regional coal deposits and did not look at the coal market as an integrated national and international entity. The State of Illinois has, in recent years, taken a more comprehensive approach to the solution of the problem.

Jan 1, 1992

By J. M. Manka

American mining companies operate many drum hoists that hoist from various depths with varying payloads. This paper will review the procedure of selecting optimum wire rope constructions for these existing hoisting installations. Selection for proposed installations along with recommended hoisting parameters will also be presented. To achieve this optimum rope performance, preventative and corrective maintenance procedures will be reviewed along with examples of rope problems and their causes.

Jan 1, 1992