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By Harry Perry

The decline in coal production has been slowed somewhat in recent years, mostly because of the industry's own remarkable success in holding the line on costs, and partly as a result of advances achieved through industry and government research. Nevertheless, the decline has continued. This downward trend combined with the increased productivity of labor through mechanization that has been necessary for coal to retain even its present competitive position, has resulted in a serious reduction in the number of miners required and large scale economic dislocations in mining communities. For coal to regain a more favorable position it must either expand existing markets by reducing the cost of the delivered product and thereby compete more effectively with other fuels or develop new uses that will require large tonnages of coal. New markets involving several million tons, which would look extremely attractive to most other United States industries--including the organic chemical industry--would do little to alleviate the coal industry?s depressed economic conditions, While such small new markets would be welcome, an industry producing over 400 million tons per year must look to large tonnage outlets for solutions to its long range economic problems.

Jan 1, 1964

By Kenneth S. Johnson

High-purity gypsum of Permian age crops out in three major gypsum districts of western Oklahoma. The northwest and southwest districts have important reserves in the Blaine Formation, whereas reserves of the west-central district are in the Cloud Chief Formation. Gypsum beds of the Blaine Formation typically are 10 to 30 feet thick, 95 to 99 percent pure, and interbedded with shales that are 2 to 30 feet thick. The base of the Cloud Chief Formation consists of a massive bed of gypsum that typically is 20 to 100 feet thick and is 92 to 97 percent pure. Anhydrite is present in the sulfate beds, beneath 20 to 100 feet of overburden, at a number of places in all three districts. Total gypsum reserves in the three districts are estimated at 48 billion short tons. These reserves are well suited for open-pit mining or quarrying, because gypsum typically forms hills in the semiarid climate of western Oklahoma, and the gypsum layers are nearly flat lying, without folds or faults. Seven companies currently mine a total of 1.0 to 1.4 million tons of Oklahoma gypsum each year for wallboard, for plaster, as a retarder in portland cement, and as a soil conditioner.

Jan 1, 1978

Overview In 1992, US coal supply and demand were shaped more by weather conditions and the export market than by the economic recovery. Preliminary data compiled by the Energy Information Administration (EIA) (Table I) show that coal production declined slightly to 902 Mt (994 million st). Consumption, though, rose by about 1 % to 811 Mt (894 million st), trailing the 2.1 %growth in Gross Domestic Product. Contributing to the decrease were a sizable drop in coal exports and some coal stock withdrawals. Consumption increased largely because electric utilities turned to coal to offset a shortfall in hydroelectric generation caused by a drought in the Northwest. Apart from this, the demand for coal-fired generation was dampened by a mild winter in the northwestern and northcentral United States, and a cool summer in the central and eastern parts of the Nation. Coal use by other consumers was about the same as in 1991. The average delivered prices of coal to all consuming sectors decreased slightly in 1992, reflecting soft coal markets (Fig. 1). US coal exporters experienced a set-back in 1992 mostly because of losses in the European market. Total coal exports fell by 6% to 93 Mt (103 million st), the first decline since 1987. Coal stockpiles at the end of 1992 were about 1.8 Mt (2 million st) below 1991, despite stock buildups by some electric utilities in the East. Stocks were built up as a hedge against possible coal miners' strikes after the Feb. 1, 1993, expiration of the contract between the United Mine Workers of America and the Bituminous Coal Operators' Association.

Jan 1, 1993

By J. Allen Hennessy

INTRODUCTION The increasing price of gold and silver over the past 10 years has caused increasing activity in the exploration, evaluation and development of precious metals projects. Many of these deposits are relatively low grade and short lived which makes them economically sensitive to the major project variables such as metal price, capital cost, operating cost and of course, tonnage and grade. These deposits often have a high variability (a coefficient of variation -- o/u -- of 2 to 5) and an intermixing of ore and waste, making ac- curate ore reserve estimation difficult, especially when using traditional estimation techniques. Often, the estimation errors are not the 10-20% that we see in base metal deposits, but the errors in grade and tonnage can be as high as 50%, which can obviously have a very substantial impact on project Recent developments in geostatistics when coupled with a sound geologic under- standing of the deposit can significantly improve reserve estimates of these variable precious metals deposits. Examples will be given of actual deposits where the traditional estimates were significantly different from the mining reality. An attempt will be made to explain the applicable geostatistical tools with a minimum of geostatistical jargon and without complicated formulas. The key to improving the reserve estimates is a clear understanding of the deposit geology and especially the structural controls, the use of local estimation techniques that recognize the intermixing of ore and waste and the effect of selective mining on recoverable reserves, and the use of a global reserve estimation technique to check the results of local estimation. Geologic Controls The vast majority of gold and silver deposits being mined or developed in the western United States would be classified as epithermal deposits. These are formed by hydrothermal fluids (hot water) flowing upward through the rocks and depositing the precious metals as the fluids cool or reach areas of lower pressure or favorable chemical sites. These environments are similar to present day hot springs-type environments with some deposits being clearly associated with surface hot springs such as the Homestake McLaughlin deposit in northern California. These hydrothermal deposits can occur in sedimentary rocks resulting in deposits such as those of the Carlin district or the Jerritt Canyon deposit or the hydrothermal systems can occur in volcanic rocks forming deposits such as Round Mountain, Manhattan or Paradise Peak. The mechanisms of formation were similar in either case with the solution flow controlled by geologic structure and precious metals deposited when the conditions of temperataure, pressure and chemical environment were favorable. The gold and silver hearing solutions travel through permeable faults and fracture systems depositing the metals along these channels. The grades are often highest in the central parts of these conduits (veins) with lower grades in the surrounding rocks. An understanding of the nature, distribution and orientation of these plumbing systems is important to a realistic reserve estimate. The point to be emphasized here is that, good, sound geology in the form of geologic mapping, logging of rotary chip samples and a few carefully logged core holes can signifi- cantly improve an ore reserve estimate.

Jan 1, 1987

By Richard J. Wilson

The importance of coal as a major source of energy used by the steel industry has been increasing due to the gradual changeover from steel- making by the open hearth process to steelmaking by the basic oxygen process. Since the production of steel by the BOF process increases the demand for hot metal, there is a growing need to ensure the supply of coke required for the production of hot metal. Coal used for cokemaking has become, therefore, an increasingly important raw material for the steel industry in recent years. Our current projections indicate that coal will be the source of 71% of the total energy requirements of Inland Steel Company in 1985. As a result of the energy shortages of the last few years, various conservation programs have been initiated by the steel industry to reduce the consumption rate of fuel. The efforts to conserve energy have been successful to a great extent due to the rapid advances made in the technology of ironmaking that facilitated gradual reductions in the quantity of coke used per ton of hot metal produced in the blast furnaces. The decrease in the consumption rate of coke was made possible by the use of improved raw materials, such as iron ore pellets and fluxed agglomerates, the operation with high blast temperatures, the injection of auxiliary fuels, and the enrichment of the blast with oxygen. It is expected that additional reductions in the fuel consumption rate will be possible in the ironmaking operations of the large blast furnaces that are being equipped with facilities for proper burden distribution and for operation with higher blast temperatures at high top pressure. The purpose of this paper is to show the effects of coke quality on the production of BOF steel. The importance of coke quality will be pointed out by discussing the effects of the physical strength of coke on both the blast furnace productivity and the steelmaking operations of an integrated steel plant, such as Inland Stee1 Company.

Jan 1, 1980

By A. T. Yu

The broken hill proprietary company Ltd., Australia's only steel producer, has come a long way. Since 1885 to reach today's. Capacity of 6.6 million long tons of ingot steel per year.* its Newcastle steel complex in New South Wales, located 100 miles north of Sydney and on-stream since 1915, has likewise shown continued impressive growth (fig. 1). The most recent expansion plans at Newcastle call for sub¬stantially increasing its production, with the help of some added facilities, but principally relying on the increase in efficiency of the furnace operation. Its modern raw materials blending system will playa major role in meeting Newcastle's new targets.

Jan 1, 1969

By Robert C. Salak

The era of low-seam mining with continuous haulage has been here for quite some time. Typical tonnages in companies such as Terry Glenn Coal are currently averaging 405 tonnes per shift in .8m coal. JoAnn Coal has averaged 453.6 tonnes per shift in .775m to .825m coal for the past four years. John Chaney of Chaney Coal has averaged 297 tonnes per shift in .6m to .65m coal. There are many other mines that are experiencing similar success and with maintenance costs that are averaging $.10 to $.40 per tonne. These figures have been documented and can be verified by the operators.

Jan 1, 1981

By Norman Haber

The Haber Gold Process (HGP) is a proprietary. hydrometallurgical extraction methodology that was developed in 1983-1984 by Norman Haber and Dr. John Lee of Haber, Inc., a small public company in Towaco, New Jersey specializing in hydrochemical process development for precious metals. It was pilot tested repeatedly in 1985 at our pilot plant in Tombstone, Arizona, with different types of gold bearing mineralization. Both Pincock, Allen and Holt (USA), and PA Technology (Australia) were involved with some of these pilot tests. The ores tested included easily cyanide-extractable oxide type gold ore from Australia, marginal heap-leach type ore from Cripple Creek, USA, and a hematite bearing ore from California. In all cases, extraction time was 6 hours or less yielding 90-99% recoveries of assayed gold values. The HGP operates as a lixivient which parts the gold from the rock matrix, yielding gold in solution in a fully recoverable form. Both precipitation methods, such as zinc participation or Carbon in Leach systems ( or Carbon in Pulp) have been shown to be feasible with this technology for the recovery of gold from the pregnant solution. Both batch vat leaching as well as continuous processing are realistic for use with the HGP. It has also been considered that the HGP might also benefit heap leaching due to several advantageous factors over cyanide. One such consideration is that the HGP can operate effectively with acidic ore types. The use of cyanide with such ores often requires attention to pH and neutralization with lime. This tends to reduce and even clog the permeability of the leach bed.

Jan 1, 1998

By M. Kawulak

The necessity to protect the environment can limit mining activities and make some areas less attractive for the prospecting and exploration of mineral deposits. In Poland, the main environmental factors that restrain Irumng are: 1. Regional A Protection of the landscape B. Protection of ground water from contamination and depletion 2. Local A Conservation of fertile soils B. Conservation of forest resources C. Preservation of natural, cultural, and historical monuments The regional factors listed above that can limit mining are presented on a map of Poland. These data, combined with maps of known and potential mineral deposits, make it possible to delineate general levels of limitation for various mining-related activities varying from "no existing environmental limitations" to "no allowed industrial activity" As an example, a compilation of such data is presented for lignite exploration and mining in Poland. Lignite deposits occur within Upper Paleocene to Upper Miocene clastic strata at depths ranging from a few to 300 m. The thickness of the lignite is generally a few meters, but can locally reach over 100 m within grabens. As a result, the overburden-to-lignite thickness ratio varies from less than 1 to over 20. Within the same Tertiary strata, and within overlying Quaternary strata, several aquifers exist that produce good quality water that may be contaminated or depleted during lignite mining. The protection of these ground waters is the main factor limiting lignite mining and should be addressed in mining and environmental policy and planning.

Jan 1, 1996

By John Hughes

Fundamental to the use of rotary bit drilling equipment for oil and gas drilling is the requirement to maintain a cooling and lubricating environment for the bit and a means of conveying the cuttings from the drilling operation to the surface. The vast majority of such functions are provided for by the use of water based drilling fluids, commonly known as the drilling mud. One of the basic constituents of drilling mud is bentonite, a montmorillonite clay. Bentonite, when mixed with water at approximately 6% solids, will produce a fluid which has several important features in connection with its role as a drilling mud:

Jan 1, 1983

By W. J. McDonough

Rapid growth and acceptance of engineered materials have changed the way we live. We have come to expect improved performance at less cost. At the same time, our awareness of societal and environmental issues created by these materials during and after their lifetime has been heightened. As a result, material lifecycle analysis is receiving considerable attention. Material lifecycle analysis evaluates the cost/effective tradeoffs at each stage of a material's life: feedstock, fabrication, performance, recycle, and disposal. The U.S. Bureau of Mines investigates a material's lifecycle using technical cost models augmented with decision and impact analyses. Results of these studies are useful in gaining a better understanding of current material selections and illustrating the multifaceted issues associated with engineered materials in today's society.

Jan 1, 1992

By H. Nemutolluhi

Discussion by G.E. Agar In the April issue of Mining Engineering there is a technical note "New size laboratory ball mill for Bond Work Index determination" written by M. Nematollahi which is very confusing. My recollection is that a description of an experimental procedure should be such that someone skilled in the art should be able to reproduce the results. Applying this test to this particular article would according to me cause a failure to be registered. There are apparently three batch laboratory test procedures referred to in the article. One of these is the traditional Bond test with all its limitations such as dry grinding followed by exclusively dry screening, two attributes which fail to simulate conventional industrial grinding. There is a second procedure (NSBM) which the author is advocating as an improvement of the Bond procedure but from the description I doubt that anyone would be able to repeat the procedure. For instance, is the grinding to be done wet or dry, if wet at what pulp density, and how is the screening to he done, wet or dry or a combination? On top of that uncertainty the author refers to a simplified "Anaconda" test. No reference is provided for this procedure and in the text the results of the technique are referred to "Denver wet ball mill" results and say nothing of Anaconda results. Reply by H. Nematollahi I think that the method proposed to determine the Bond Work Index in this paper is clearly described in the paper as follows: •The method of grinding is dry (Ref. paragraph I, subject Method description); •The size of ball mill, the quantity and size of balls are noted (Ref. paragraph 1, subject Test equipment); and The test procedure is described in detail (Ref. paragraphs 1, 2 and 3, subject Test procedure). As it is noted in the paper, the test has been worked out under the same condition as Standard Bond Test with ball mill, so dry (screening should be dry also), but using a smaller ball mill and a smaller quantity of sample. Considering the above mentioned points, I believe that the method has been fully and clearly described and it ought to be repeatable as well. The Anaconda test is a method for determination of Work Index and could be done by any types of laboratory wet ball mill (Yan, R.F., et al., cf. References). I applied this method using a laboratory Denver ball mill (Ref. paragraph I subject Determining the Bond Work Index). So the results referred to Denver wet ball mill can be equated the same as Anaconda method.

Jan 1, 1996

By Emily Muto

LiDAR technology has made it possible to map large areas of underground mines accurately and rapidly in three dimensions. MSHA Technical Support began implementing LiDAR technology in conjunction with the Agency’s Pillar Collapse Initiative, using scans to determine width-to-height ratios (w/h) of pillars adjacent to mass collapse areas and to conduct risk assessments for global pillar stability in U.S. stone mines. This work quickly expanded to include change detection, such as measuring many pillars to show which are deteriorating over time. Change detection has also been used in ground falls and squeeze areas to see if they have continued to propagate. LiDAR technology supports accurate data acquisition of unstable mining conditions from safe distances. For example, once the LiDAR scan has been processed, it can measure roof fall cavity heights and volumes with the user at a stable ground location. Some LiDAR scanners can collect geologic data, such as joint orientations.

Jun 25, 2024

By Qiong Wu, Qinghua Gu, Yichuan Lv, Jin Yuan, Caiwu Lu

"The cut-off grade is one of the important parameters of mining production. Different material cut-off grade is directed to different destinations. Based on reasonable and optimal cut-off grade, long term mining plan and investment decision analysis can be made for mining managers. In view of multiple-metals open-pit, the paper has proposed that multiple-metals cut-off grade optimization model is set using the objective function to maximize net present value (NPV). The method of equivalent coefficient calculation is proposed to convert multi-metals cut-off grade optimization to a single metal cut-off grade optimization. Then the optimization model is applied in a molybdenum and tungsten large open-pit mine in china. The parameters of concentrate price are calculated by PRT in the model and the curve of grade-recovery rate is analyzed and studied according to actual production data. Based on 3D metal deposit model, the distribution of grade-tonnage is analyzed. At final step, an optimal cut-off grade is proposed to guarantee to maximize NPV. The example shows that the model of multiple-metals cut-off grade optimization can provide reasonable analysis for optimal multi-metals cut-off grade and develop optimal production strategies. Introduction Cut-off grade is one of the most important parameters in metal ore mining because of its influence on the overall economic profit of mining production. Along with the development of the mining production, dynamic optimization of cut-off grade is necessary through the analysis of technical economy. It is better to manage the mining production according to the variation of market. The cut-off grade plays an important role in mining production."

Jan 1, 2017

By J. T. Kline

This paper will present a review of the underground leaching of remnant copper mineralization left as a result of the block cave mining operation at the Lakeshore Mine in Casa Grande, Arizona.

Jan 1, 1985

By W. K. Tolley

The U.S. Bureau of Mines (USBM) is currently investigating the electrochemistry of mineral flotation. A significant need in this area is greater reliability of sensors. The USBM is testing electrolytic methods to clean and condition redox-sensing electrodes to improve the reliability and extend the service life of these instruments in the harsh physical and chemical environment of mineral processing slurries. A novel method for removing scale from fouled electrodes has been developed that includes anodic polarization to 1.2 V versus the Ag/AgCl reference potential, followed by brief potentiodynamic conditioning. Laboratory results show that this technique removes calcarious deposits from gold sensing electrodes and returns the electrode to useful service within approximately 10 min. Mechanical abrasion to remove the scale is thereby avoided.

Jan 1, 1994

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

By J. R. Gaw

Recent events pertaining to U. S. energy needs and development of alternative energy fuel resources have made the American public more aware of past and present coal mining operations, and their impacts on the nation's economy and environment. This awareness has developed rapidly due to increased government involvement and consequent media coverage. This is true particularly in the Western states and in Texas. One of the consequences of this increased public awareness is public concern over the perceived and real consequences of mining operations. Emphasis has been placed on potential releases of toxic and hazardous substances, and possible carcinogens. The result of this public concern is a mounting effort at both state and Federal levels to promote stricter laws regulating the mining industry.

Jan 1, 1992

By G. K. Roset, L. R. Woodland, J. A. Stevenson, G. J. Hodges

The Stillwater Mining Co. (SMC) is a partnership of Pittsburg & Midway Coal Mining Co. and Manville Corp. Since the summer of 1990, SMC has operated a precious metals smelter at Columbus, MT for further upgrading of concentrates from its platinum-palladium mine. The facility's gas-cleaning system 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 the design parameters. Also discussed are the startup problems encountered and their solutions.

Jan 1, 1993

By M. A. Schimmelpfennig, A. D. S. Gillies

M.J. McPherson Having worked on the thermodynamics of air/liquid-water mixtures passing through the surface fans of deep mines, I find this paper of great interest and congratulate the authors on producing it. There are two matters, however, deserving discussion. First, the authors have described the classical theory of fog formation with fogging occurring at "supersaturation." In fact, the process of fog formation begins well below 100% humidity. The more strongly hygroscopic nuclei in the atmosphere will attract water molecules and begin to grow at a relative humidity perhaps as low as 70%. The process is a dynamic one with both condensation and evaporation taking place throughout the mixture on microscopic liquid surfaces. As saturation is approached, the rate of condensation accelerates rapidly producing the familiar reduction in visibility. Hygroscopic nuclei are present in all natural atmospheres and under the appropriate conditions of pressure and temperature, will produce clean fogs. However, if the air is polluted by particulates from combustion or other processes then the resultant coagulation with growing liquid particles may produce dense (and sometimes photochemical) smogs. It is this process that is likely to occur in underground mines when moist air is cooled below dew point. Second, the authors have summarized very well the individual measures that might alleviate the problem. In particular, I agree that neither heating nor refrigerating the air, by themselves, provides a satisfactory solution. However, there is a combination of these that provides a neat and effective control of fog formation. This involves a small, self-contained refrigeration unit within a duct but without the usual external heat rejection facility. The air is cooled below dew point and, hence, dehumidified on passing over the cold evaporator coils. The heat from the condenser is rejected back into the air downstream from the water eliminator, as shown in Fig. 1. The duct configuration can be designed to create good mixing at the outlet. I have used a climatic simulation program to illustrate the effect, assuming a 500-m (1,640 ft) long airway of cross section 60 m2 (645 sq ft), an airflow of 9 m3/s (318 cu ft per sec), inlet conditions of 19/19.25°C (66/67°F) wet bulb/dry bulb temperatures, a virgin rock temperature of 17°C (63°F) and typical rock thermal properties for a hard-rock mine. I have also assumed that 10% of the rock surface is wet. Figure 2 shows the variation in temperatures along the airway if no measures are taken. The relative humidity remains close to 100% and condensation will occur throughout the length of the airway. Before any such installation is designed, the exercise must, of course, be repeated for each location with accurate data. However, this example demonstrates the potential of the system. The idea is not new - the principle is sometimes used in air-conditioning plants for buildings. Figure 3 shows the effect of removing 30 kw of heat by evaporator coils sited 40 m (131 ft) along the airway and rejecting that heat (plus another 10 kw of compressor and fan power) into the air at 60 m (197 ft). Condensate water is produced, at a rate of 0.45 L/min (0.12 gpm). The result of this sequential cooling/dehumidification/heating process is to separate the wet and dry bulb temperatures along the length of the airway. The relative humidity increases from 80% at the duct outlet to 92% at 500 m (1,640 ft). The airway is maintained free from fog.

Jan 11, 1983