Search Documents

By B. L. Bobo

To ensure the continued growth and economic viability of the Western coal industry, both in the domestic and inter- national markets, it is essential for the industry to become more creative and active in confronting the most serious obstacle in this objective; and that is, the inherently long distances which Western coal must be transported inland to reach its major markets. Figure 1 shows the 1982 coal consumption by state for those states where Western coal was consumed. (Except as noted in this paper, Western coal producing states are defined as Colorado, New Mexico, Arizona, Utah, Wyoming, Montana and North Dakota. Any exceptions used will have only an insignificant effect on the content of the paper). This figure illustrates the long distances that are required for Western coal to reach its markets. The total production for 1982 from the Western coal producing states was approximately 220 million tons, of which only 85 million tons was consumed within the boundaries of these states. The remainder was transported to markets outside the area. This map also shows, based strictly on the consumption of the states to which Western coal was shipped during 1982 and not considering other factors which are involved in the marketing of coal, the total market potential of Western coal would amount to a total of 445 million tons. This does not include export coal from the West Coast, which is now estimated to be less than 2 million tons for 1983. In 1980, it had been estimated that by 1985 the West Coast exports would have been at least 10 million tons per year, which will not be attained.

Jan 1, 1983

By G. Tiess, S. Mujiyanto

Indonesia is a fast growing democratic developing country comprising more than 17,000 islands, founding member of ASEAN and a member of the G-20 major economies. It is one of the most highly mineralised countries in the world, the mining sector playing a pivotal role in the country's economy. In 2001, the Decentralization Law No. 22/1999 came into force and caused a transfer of authority and responsibility from central to regional and local administrative governments. The new Mining Law of 2009 substituted its 40 year old predecessor, but lacked detailed regulations for its implementation. These were only issued in 2010, which lead to a period of great uncertainty for investors in the mining industry. The new legislation intends to foster domestic economic development, which may be interpreted as protectionist policy. For the development of a sustainable mineral resources policy, further endeavours will have to be made.

Jan 1, 2011

By F. -J. Wodopia

Sustainability of energy supplies has been an issue of general interest for a long time. Whilst in the past the continuous productive use of natural commodities was in the fore, its compatibility with the environment and climate and ultimately also social aspects have recently gained more and more attention. Today many discussions focus on the climate compatibility of individual options to act. Fossil fuels, in particular coal and lignite, are generally challenged because coal use makes a significant contribution to global man-made CO2 emissions. The drastic increase in the consumption of fossil fuels is not explained by the fact that coal utilisation technologies are not or cannot be sustainable but rather by the growing world population and the endeavours numerous national economies trying to catch up economically. Coal is the world’s No. 1 fuel and, in the view of many experts, will keep this position also in the foreseeable future. The access to its deposits plays a significant role for the economies of the emerging countries. Consequently the aspects of energy security and economic efficiency need to be considered at eye level with climate compatibility. In Germany, however, the public acceptance of fossil fuels and of large industrial projects is in the focus of attention.

Jan 1, 2011

By J. L. Cupp, R. C. Ford, B. R. Romig

The Climax Molybdenum Mine, located near Leadville, Colorado, is the site of a lengthy mining history spanning more than 80 years. In the 1960’s, extraction of molybdenum from oxide ore located adjacent to the massive molybdenite sulfide deposit resulted in the construction of an earthen core dam to impound fine-grained oxide tailing in the Eagle River Valley. Through recognized value of water storage and reclamation opportunities, a tailing removal project was initiated in 1993 to convert the impoundment facilities to a post-mining beneficial land use of developed water resources. An evaluation of the effect residual materials and lake dynamics would have on in-stream water quality was performed. Eagle Park Reservoir stands as a model for future reclamation efforts that involve water delivery to highly sensitive receiving waters. This paper provides a case study on project development, the evolution of water quality assessment, and the regulatory framework that contributed to this project’s success.

Jan 1, 1999

By L. S. Harris

The application of briquetting in various chemical, mineral, mining and metallurgical processes has been rapidly increasing in the past two decades. This is, in part, due to the development of new, more economical and higher performance briquetting equipment. Some of these developments, which have reduced the operating and maintenance costs,, include anti-friction bearings, hydraulically applied pressure enclosed and sealed gearing and bearings, tapered predensification feed screws, water cooling and materials of construction capable of operating at temperatures up to 18000F, and control systems capable of maintaining optimum briquette quality control. The briquets can be formed into almost any desired size and shape, To date, with present rotary briquetting presses in the 25 to 500 ton force range, briquets from 1/4" to 6" length are presently being used, some of which are illustrated in Figure No. 1. In force fed rotary briquet machines, these shapes are produced by feeding the material in between a pair of counter rotating rolls, as illustrated in Figure No. 2. The rolls have forming dies indented into their circumferential surface, as illustrated in Figure No. 3.

Jan 1, 1973

By Thomas B. Borak, Keith J. Schiager, Janet A. Johnson

INTRODUCTION Several major factors introduce uncertainties into the assessment of radon progeny exposure to miners using time-weighted average radon progeny concentrations: uncertainty in the measurement of radon progeny concentrations in specific areas, assignment of an individual miner's time to those areas, variation in radon progeny concentration between measurements and potential human errors involved in calculating concentrations and handling data. The currently available grab-sampling methods for determining working level were analyzed to determine the magnitude of the uncertainty due to each of these factors. For all measurement methods studied, the variation in the airborne concentration with time in operational areas of a mine is the dominant factor in the uncertainty in determining annual radon progeny exposures for individual miners. Uncertainties relating to accuracy of the method and precision of measurement were found to contribute a significantly greater portion of the total uncertainty than human errors. Under normal conditions, if the technicians performing the measurements are conscientious and well trained, human error contributes little to the total uncertainty of the radon progeny exposure determination. The primary goal of radiation monitoring is the reduction of radiation exposure to the lowest reasonably achievable level below regulatory limits. Monitoring personnel in mines should be trained not only to obtain accurate estimates of miner radiation exposures but also to recognize and, when possible, to implement correction of situations which result in unnecessarily high radon progeny exposures. ESTIMATION OF UNCERTAINTY DUE TO HUMAN ERRORS Human errors affecting the assignment of annual radon progeny exposure to individual miners can be placed in two categories: those related to the measurement of radon progeny concentration in specific mine areas and those related to estimation of occupancy time for individual miners and transcribing data to permanent records. The former are specific for the measurement method used; the latter are common to all methods. Errors in Determination of Working Level All systems for determining radon progeny concentration require measurement of several parameters, which include volume of air sampled, count rate and decay time. These quantities and appropriate constants are used in a basic equation, specific to the system, which estimates working level. An unintentional random mistake in measurement of any one of these parameters or in the selection of proper constants will contribute to the uncertainty in the determination of working level. In our analysis of human error we separated each measurement method into a sequence of independent operations, with each step subject to operator error. For each operation we estimated the probability of occurrence and the consequence of errors to obtain a resulting uncertainty. Certain types of errors result in specific consequences. For example, we assumed that an error of 5 seconds in timing of a 5-minute sample results in a fractional error of 1/60 (1.7%). Other types of errors can result in a range of uncertainty. Transposing digits read from a scaler can produce errors ranging from near zero to approximately 60%. In these cases we calculated the statistical variance for the distribution of errors. We assigned the square root of the variance divided by the mean as the consequence factor for that type of error. This is essentially the same as a coefficient of variation. The product of the probability of occurrence and the consequence factor is the fractional uncertainty in the measurement due to that particular error. The total uncertainty due to human errors is calculated by taking the square root of the sum of the squares of the uncertainties generated by all manual operations. Uncertainties Due to Human Error for the Kusnetz Method One of the techniques most commonly used to estimate working level in U.S. uranium mines is the Kusnetz method. A generalized way to express the equation used to compute WL by this method is: WL = (Net Alpha Counts)/(V)(ST)(CT)(E)(K) where: V = sample flow rate in liters/min ST = sampling time in min CT = counting time in minutes E = absolute counting efficiency K = Kusnetz conversion factor (dis/min-L per WL), as a function of decay time in minutes. The example of human error analysis presented here is based on the Kusnetz procedure having a timing sequence of 5 minutes sampling time, 40 minute decay time, 2 minute counting time. During the sampling procedure a stop watch is used to determine the timing interval. We assume that it is common to make small timing errors of a few seconds, but larger timing errors occur infrequently. Errors greater than 30 seconds are considered to be essentially non-existent since we assume that the

Jan 1, 1981

By S. Garcia, J. Gebhardt, D. McBride, A. Hernandez, A. Esplín, M. Cross

The Minera Yanacocha operation consists of several heaps interconnected with ponds and gold recovery plants and presents various operating challenges. A comprehensive process model has been developed in order to better understand the effects of certain operating parameters and inventory issues. An integral component of the process water/mass balance is a model of each heap that describes heap behavior based on the individual characteristics of the heap. The heap models are linked to a mass balancing program in order to track flows and concentrations throughout the circuit. A case study of the process heap model is presented for the La Quinua heap, including results for the normal base line operation and several operational problems such as loss of solution flow to the heap (i.e., pump failure), increased flow to a section of the heap (i.e., pond volume control), effect of significant rain events, and impact of a change in material properties (i.e., change in ore type). The impact on heap operating efficiency is discussed with regard to effects on recovery and gold solution grades.

Jan 1, 2007

By J. P. Matoney

In recent years, the diminishing supply of natural gas has led energy suppliers and consumers to consider making synthetic natural gas from coal. A number of processes have been devised to produce gas from coal; many of these have been operated at the pilot stage and some have been operated commercially. Each process has specific coal feed stock requirements with respect to size consist and moisture content. The purpose of this presentation is to compare the estimated costs for coal handling, live storage, size reduction and drying facilities that would be required for delivery of coal feedstock to different gasification processes.

Jan 1, 1977

By P. O. Ripley

Into this tumultuous twentieth century, every second, two new babies are born. This is 5,412 per hour, and 130,000 per day. Relentlessly, consistently, alarmingly, they add to the more than three billion human beings who already inhabit the earth. Every tick of tier clock brings with it a problem child, the problem of another mouth to feed, another body to clothe, another human being for whom to provide. On the other hand, medical science has achieved a postponement of death, considerably past the period of a few years ago. Thus, life expectancy has been increased and world population has increased accordingly. Darwin (4) writing in 1962, suggests "It is curious how long the world is taking to perceive that we are living in what is a fantastically abnormal period of history, and one which must inevitably end soon, The first warning note of a possible population explosion was given by Malthus in 1799". He suggested that population increases geometrical while production increases only arithmetically and that soon we would not be able to feed the rapidly increasing population.

Jan 1, 1966

Coal bursts are one of the least understood yet the most critical hazards in underground coal mines. The ground motions induced by seismic events can trigger unstable failure of coal and rock mass and degrade the surroundings of an excavation. Therefore, the characteristics of ground motions should be fully investigated for an improved burst risk management. This paper analyzes ground motion features of a longwall panel from a typical underground burst-prone coal mine in China. The results showed that most of the ground motions on roadways were hardly initiate coal bursts due to insignificant energy input to the damage. The intensity of ground motions in near-field zone were nearly 20 times higher than those in far-field zone. The strongest vibration on roadway was induced by a coal burst with energy of 28,600 kJ, which can cause ground motion of 0.77 m/s and equivalent dynamic stress of 14.69 MPa. The findings of this paper can improve the assessment of seismic risks and its management.

Jan 7, 2020

By J. Kemeny, J. Lyons-Baral

"Point cloud technology is now an indispensable tool in geological and geotechnical data collection, interpretation and analysis. Open-pit and underground mines of all sizes are regularly collecting point cloud data as laser scanning (LiDAR) and photogrammetry surveying devices have become affordable and the workflows fast and efficient. Past challenges of large data processing and manipulation are gone with recent technological advancements in computer hardware and software. These innovations reduce file sizes, ease rendering requirements and allow for the implementation of real-time 3D viewers and surface meshing tools. With its ability to remotely and safely, rapidly and accurately extract large quantities of georeferenced and 3D-oriented data, point cloud technology provides numerous applications to the geomechanical field. The list of uses is continuously growing. This article specifically focuses on digital outcrop modeling and digital terrain engineering. Point clouds. The high-resolution and increasing availability of point cloud technology is rapidly improving open-pit and underground mines’ investigation, interpretation and characterization of site geology and rock mass properties (Kemeny et al., 2015; Lyons-Baral, 2012). LiDAR and photogrammetry are common remote sensing methods employed to measure the coordinates of surfaces in three dimensions (3D), providing the X, Y and Z locations and typically the reflective intensity and/or the visible three-band color of each point (Fig. 1).LiDAR uses either a time-of-flight or phase-shift measurement of a laser beam reflected off targeted surfaces and received back into the device.Photogrammetry generates point clouds by merging multiple overlapping photographs and uses stereographic plotting to define the locations of object points in 3D space. These methods can be deployed from airplanes, unpiloted aerial systems (UAS or drones), tripods, land vehicles and even in a mobile backpack shown in Fig. 2. RADAR, Total Station-Prism and other remote sensing systems also offer very precise “point clouds,” but this article does not address these due to their higher cost and lower versatility and mobility."

May 1, 2016

By J. Kou

The adsorption process, density and structural property of the oleate layer adsorbed onto a hydroxyapatite (HAP) surface at six different concentrations and three pHs (pH 8, 9 and 10) have been studied using the technique of quartz crystal microbalance with dissipation (QCM-D). The present study demonstrated the versatility and accuracy of the QCM-D for surface adsorption characterization. The real-time measurements of frequency and dissipation shifts with a hydroxyapatite-coated sensor revealed changes in the hydroxyapatite surface during the entire adsorption process. Chemisorption and surface precipitation of sodium oleate were also observed on the surface of hydroxyapatite through the use of Fourier Transform infrared spectroscopy(FTIR). Chemisorption dominated at low concentrations and high pH values and formed a rigid and thin adsorption layer. Surface precipitation of calcium oleate and micelles dominated at concentrations higher than critical micelle concentration (CMC) and lower pHs and formed a thick but dissipated adsorption layer with a high hydration level. Three distinct adsorption behaviors were identified from the different slopes of ?D-?f plots. The adsorption density was less than a monolayer at concentrations <0.164 mM, but increased significantly at concentrations higher than 0.821 mM at all three pHs. The critical concentration at pH 8 was 0.33 mM, which was lower than at pH 9 (0.821 mM) and pH 10 (3.3 mM).

Feb 1, 2012

By F. W. Brackebusch

In the paper presented by F.W. Brackebusch on the "Basics of paste backfill systems," paste fill was presented as a backfill process that offers many advantages over other alternatives such as hydraulic fill and rock fill. It was observed, however, that the mechanics of paste-fill transportation in pipelines is not fully understood and that the success of its implementation in practice depends on the precise control of the proportions of fines, aggregates and water in the mixture. The author emphasized the necessity for laboratory and full-scale testing to determine the suitability of a material to be used as paste fill. Although experimental testing is definitely an important operation in the design of a reliable paste fill, advances in the understanding of the fundamental laws that govern paste flow in pipelines are equally relevant. Ideally, the results of such efforts would provide predictive models for the rheology of the paste and the corresponding pumping-energy requirements. In an attempt to achieve this objective, an ongoing research program has been active at McGill University&apos;s Department of Mining and Metallurgical Engineering. Preliminary results showed that the underlying mechanics of paste-fill flow in pipelines may be described in terms of what is known as "plug flow," as depicted in Fig. 1. Although this flow mechanism has been known qualitatively for many years, few attempts managed to offer a comprehensive model (Gandhi, 1987; Duckworth, 1986). In our model, it is assumed that coarse aggregates present in the mixture form a porous core, which is filled with paste (fines and water) and is surrounded by an annular non-Newtonian (Bingham-plastic) lubrication layer, which enables the mixture to flow with pressure losses that are easily overcome by common positive-displacement pumps. In summary, our model predicts the thickness of the annular lubricating layer, which controls the magnitude of the pressure losses. This is done either by collecting data on the apparent viscosity of the Theologically-active fine fraction and using an analytical equation (Bouzaiene, 1994), or is done by measuring the void content of the coarse aggregates and deducing the thickness as a function of the fine- to coarse (weight or volume) fraction ratio in the mixture for a given pipe diameter and solids concentration. Our model predictions showed good agreement with data from Duckworth et al. (1986), as shown in Fig. 2.? References Bouzaiene, R., 1994, "Hydraulic transportation in mining," Ph.D. dissertation in progress, McGill University, Dept. of Mining and Metallurgical Engineering, Montreal, P0, Canada Duckworth, A., Addie, G.R., and Maffei, J.R.,1986, "Mine waste disposal by pipeline using a fine slurry carrier," Proceedings of the 11th International Conference on Slurry Transportation, Slurry Transport Association, Washington DC. Gandhi, R.L., 1987, "Effect of rheological properties of fines fraction on slurry hydraulics," Proceedings of the 12th International Conference on Slurry Technology, New Orleans, LA.

Jan 1, 1996

An incremental analysis based stope design optimization method was developed at Exodus, an underground project located 30 miles north of Carlin, Nevada. Traditional underground stope design methods, by manually drawing stope shapes, are typically very time-consuming and lacking of consistency and accuracy. For quick reserve calculation and economic analysis, a new method named &apos;3D Incremental Analysis based Stope Optimization&apos; was created for mine wide stope designs at Exodus. With this unique but practical method, multiple options of mine designs were completed within a short period time, which allowed us to select the optimal cutoff grade and best stope design option for the project.

Jan 1, 2012

By P. J. Suardini, T. E. Seppanen, M. J. Hanninen

In order to reduce the heat loading in the Tilden Mine kilns caused by burning coal, which in turn resulted in rapid and significant build-upon the kiln lining, internal carbon was added to the green ball prior to balling. Intensive laboratory testing led to three short-term full-scale plant tests that were successfully conducted. Appropriate environmental permits were obtained to allow Tilden to use internal carbon on a continuous basis. Findings concerning carbon addition rates, reductions in coal use, build-up reductions, fired pellet quality, and environmental issues will be discussed.

Jan 1, 2003

By W. H. Langer

The U.S. Geological Survey (USGS) in cooperation with the New Mexico Bureau of Mines is conducting an assessment of mineral resources in the 36,800 km2 Mimbres Resource Area, southwestern New Mexico. Included in the assessment is a literature-based evaluation of sand and gravel that utilizes third party geologic information. The USGS has developed a method based on existing 1:500,000 scale geologic maps supplemented by remote sensing, statistical models, and point data such as test hole or pit records. The method defines the areal extent, quality, and quantity of aggregate.

Jan 1, 1996

By S. Al-Thyabat

Conditioning of flotation feed is an important prerequisite for efficient flotation. This process depends on parameters such as conditioning time, slurry concentration and slurry pH. The objective of this paper is to optimize the conditioning process for the flotation feed. This was achieved by first conducting preliminary experiments at constant slurry pH to determine the significant ranges of slurry concentration and conditioning time. Then, factorial experimental design (32 experiments) was used to investigate the significance of the above parameters and their interactions on flotation recovery and grade. Statistical analyses using ANOVA approach showed that flotation recovery (R) and concentrate grade (g) were affected by feed conditioning. It was found that concentrate grade was linearly proportional to the slurry concentration and conditioning time, while flotation recovery was exponentially proportional to the conditioning parameters. A contour plot of the flotation response (recovery and grade) against conditioning parameters showed that the optimum operating parameters for flotation feed conditioning was a conditioning time of 1.5 to 2 minutes and a slurry conentration of 55% to 60%.

Jan 1, 2008

By D. A. Stanley

Researchers at BCD Technologies and the University of Alabama have applied three statistical techniques to the information contained in a large database of measurements from a phosphate ore processing plant. The rust, Principal Components Analysis (PCA), replaces many measured variables with a few fundamental and un-correlated variables. The second technique, Projection to Latent Structures (PLS), is an extension of PCA that explores the relation between variables identified as either independent or dependent. The third technique, Cluster Analysis (CA), is applied to the results of the PCA or the PLS calculations, and identifies individual data clusters that represent uniform operating conditions in the plant. All three statistical methods can be seen as geometrical operations on the data viewed as points in space. A Viewer gives a corresponding graphical presentation of the data points. This paper describes the use of the above three techniques and the Viewer to explore part of the phosphate flotation database.

Jan 1, 1998

By J. W. Powell

Several years prior to 1962, it became obvious that in order to develop ore reserves below the Storke Level, it would be necessary to devise a method to facilitate the ore being lifted three hundred feet to the surface or six hundred feet to the mill. The final plans called for an underground crusher complex with two stages of crushing and a conveyor belt gallery for transport of the ore six hundred feet above, to the third crushing stage. Access into the area was gained in 1962, by sinking Five Shaft approximately one quarter mile southwest of the proposed complex site, and drifting into the area. Collar elevation of Five Shaft is three hundred feet above the 600 Level Crusher Complex. All muck was loaded into ten-ton granby cars, hoisted to the surface and dumped. (See Figure 1 for the relationship between Five Shaft and the Crusher Area) Drifting into the Crusher Area contunued until 1965 at which time the Crusher Room Cutout was started. The Crusher Access Drift (CAD on Figure 2) war driven and mining pm- ceeded according to the description on drawings marked Figure 3a and 3b. After the arch portion of the Cutout was excavated and concreted, removal of the center "pillar" commenced. This muck was removed with an Eimco 123C crawler-mounted front-end loader. (See Figure 4) A total of 576,000 cubic feet of rock was removed from the Crusher Cutout. All sup- port was afforded by grouted roofbolts on a specified pattern, as shown in Figure 3c. Crane support columns were put into place and held by braces welded to roofbolt heads. Sidewalls and endwalls were formed and concreted. (See Figure 5 for the finished product)

Jan 1, 1970

The technical parametrization of reserves is a technique which has made an important contribution to the definition and the calculation of optimal mining projects. Its applications to a new open-pit optimization program have already been presented in various papers (François-Bongarçon and Maréchal (1976); François-Bongarçon and Guibal (1981)). The present paper gives a brief description of the general problem of parametrizing reserves before going into the details of the practical algorithms used in two typical cases, i.e. open-pit mining and mining between hanging wall and foot wall.

Jan 1, 1982