Search Documents

By John A. Reeves

The unit-train concept of moving raw materials .is considered by many railroad men as the most signifigant contribution to reducing rail freight costs since the introduction of the diesel locomotive. The idea, which involves assigning railroad equipment to only one haul and keeping the equipment rolling results in the maximum utilization of equipment. For example before the unit train was plaged in servige on coal hauled to one of Mid. Continent's customers, about 900 cars and 9 locomotives were needed to move the coal requirements for this plant, compared with. 250 cars and 6 locomotives used by the present scheduling of unit trains. If the economics of unit-train movements are to be achieved, coal companies no longer can use railroad cars as small storage bins on wheels to accumulate their coal in trainload shipments, but, rather, must build large bins which incorporate facilities for the rapid loading of railroad cars in a minimum length of time. In this manner railroad equipment is operated at a high degree of efficiency 'with consequent dollar savings. After negotiations between Mid-Continent, the customers and the Railroad, it was decided a unit train loadout and storage facility at Carbondale was required in order to reduce the delivered price of coal to the customers and thereby contribute to the reduction in the cost of manufacturing steel. Carbondale was selected as the bin site location, because the cost of constructing a railroad to Redstone could not be justified for the tonnages anticipated.

Jan 1, 1969

By David Oliveira

"INTRODUCTIONOne of the key drivers for the selection of a mechanized tunneling method in good quality rock masses is a good excavation advance rate. In order to achieve satisfactory advance rates, a good geotechnical performance of the rock grippers in main beam open tunnel boring machines (TBM) is required, besides other factors related to ground support and the performance of the cutter head.One well known potential issue of main beam gripper TBM is associated with the bearing capacity of the tunnel side walls while crossing fault zones or poor rock masses in general. Such a mechanism is similar to that of footings on rock and perhaps the most common problem associated with gripper performance. Depending on the quality of the rock, the rock under the gripper contact may experience significant damage and crushing (Figure 1), eventually affecting the TBM advance rate due to a lack of tunnel wall reaction/support. Such a mechanism is primarily dependent on rock quality, applied loads and gripper size.In the case of large diameter TBMs (e.g., D > 12 m), a second potential failure mechanism may arise associated with the loss of confinement within a rock pillar between twin tunnels, even in good quality rock but particularly in bedded sedimentary strata. Punching of the rock pillar may develop due to excessive shear along bedding partings and sub-vertical joints (Figure 2), particularly under a low stress environment. As a result, this mechanism is dependent on both the rock pillar width between twin tunnels and stress conditions around the tunnels, in addition to the previous factors described for the first failure mechanism."

Jan 1, 2016

By P. E. Wingrove

The Kayford, Boone and Nicholas Division of Bethlehem Mines Corporation operates a modern coal preparation plant in Van, West Virginia. Since the start-up of the Van Plant in 1976 until the summer of 1980, the refuse handling system proved to be a costly maintenance problem and a material handling bottleneck. During the 1980 two-week miner's vacation the original system, which included two screw conveyors and a drag conveyor, was replaced by an installation utilizing two Flexowall steep angle belt conveyors. This paper describes the technical and economic analysis that led to the new installation and reviews its first year operating performance. The Van facility is a heavy media plant designed to handle 127 mm x 0 raw metallurgical quality coal from the Powellton seam at a maximum feed rate of 590 TPH (metric tons per hour). Depending on mining conditions, the clean coal recovery rate averages between 50 and 65%. The plant is set up with three types of cleaning circuits. Coarse material (127 mm x 12 mm) is cleaned in heavy media baths. Intermediate size material (12 mm x .5 mm) is cleaned in heavy media cyclones. Fine coal (.5 mm x 0) is cleaned in a hydrocyclone1 froth flotation circuit.

Jan 1, 1981

By B. M. Davis

The problem of assessing uncertainty in grade estimates has been a topic of research and debate since kriging was first introduced. Use of the kriging variance was originally touted as all that was necessary in order to produce confidence limits for grade estimates. Since then the prudence of using the kriging variance for confidence interval estimation has been questioned, and techniques such as the jackknife and conditional simulation have been proposed to develop "true" interval estimates. This paper compares the differences between interval estimates produced by the three methods and makes conclusions about the performance of confidence intervals produced by the different methods.

Jan 1, 1997

By J. R. Palmes

Three coal samples, selected out of eight with well characterized surface properties, were used in flocculation tests and synthetic mixture of coal and silica was used in the selective flocculation experiments. Coal wettability and flocculant type were found to have a strong effect on the flocculation results.

Jan 1, 1993

By Z. Man, X. Zhu, Y. Xian, Y. Tao

"Fine coal separation has been always concerned. The froth flotation is not efficient in desulfurization because of the low rate of sulfide liberation from raw coal, the natural hydrophobicity caused by sulfur concentration on the surface of sulfide, and the presence of large amounts of middling feed. An efficient centrifugal gravity separator was employed to separate for Shandong –0.5mm high sulphur coal, the partition curve of centrifugal separator was obtained with conclusion that the Ecart probable error value of the separator is 0.095, the imperfection I value is 0.128. Finally, comparing with the coal flotation using progressive release method, the result shows that the effect of the desulfurization with centrifugal gravity force field based on density difference between coal and minerals are much better than that of the floatation which operates based on the difference in surface properties. It provides a efficient technical way for fine coal separation. INTRODUCTION Coal plays the most important role in the energy consumption in China. Although natural gas, wind energy, nuclear power has made great progress in recent years, but the share of coal in the final energy consumption accounts for 70-80%, which is determined by energy storage of China. Under the requirement of environmental protection, the clean utilization of coal resources becomes more and more important, and the need has already been identified. Coal washing and processing plays an important role in the process of high-efficiency and clean utilization of coal. For the separation of fine coal, flotation is a traditional method for effective separation and has been used in large scale industrial applications in coal preparation plant. However, for the separation of difficult-to float coal, especially fine oxidized coal and low–rank coal with hydrophilic surface, flotation is usually inefficient [1-3]. Although many pretreatment methods have been adopted, including grinding, microwave pretreatment, new flotation reagents, the problem of efficient separation has not been completely resolved [4-6]. Thus, an enhanced gravity separation method using particle density difference rather than hydrophobic difference was proposed for the separation of fine coal. Many research results have proved that this is a practical and effective method of sorting. R.Q. Honaker used Falcon C10 concentrator, Knelson centrifugal separator and spiral separator to clean the fine coal with size of 600*210 µm and 210*37µm, the effects of different operating parameters on the separation index was discussed. The results show that the separation density of Falcon can reach 1.6, and the Ep value can reach 0.1-0.15. This paper revealed that for the separation of fine coal with high sulfur content or fine grained content. Falcon has high separation efficiency with low cost. Separation results present in another paper showed that the desulfurization efficiency of inorganic sulfur was better than that of flotation [7-8]."

Jan 1, 2017

By T. C. Canter

Technological change is continually affecting the mining industry and the many papers being presented at this meeting reflect this fact. I fully agree that miners must remain fully cognizant of technology that can change mining costs and therefore your competitive marketplace. Despite the embrace of new technology and effective mine management techniques, the mining enterprise may not realize increased net income if the structure of the minerals marketplace is not understood. An important segment of the marketing structure for minerals is transportation. Transportation costs per ton can be much greater than the mining costs per ton and may accordingly overshadow hard earned gains in productivity. Change is greatly affecting the transportation industry but the change is driven more by governmental policy than technology. Although some technological advances are occurring in the bulk transportation business, the changes I want to address arise from policy. Policy changes have come from legislation in the 1970's culminating with the Staggers Act of 1980 and ensuing Interstate Commerce Commission decisions.

Jan 1, 1985

By Malcolm T. Wane

The subject matter of this paper, "Applied Rock Mechanics?," has its genesis in a recent field trip taken by the author. A more or less standard question asked at the mines visited was "How are you using the principles of Rock Mechanics to assist you in maintaining an efficient, safe, and competitive mining operation?" The question was couched in a number of different forms, but the intent was to determine whether or not a general theory based on reason and the scientific method was applied or whether the alternatives of tradition, intuition, ?common sense', revelation, ?shotgun methods' or authoritarianism were invoked. Perhaps two responses to this query will be illustrative of the general nature of the replies. At operation XYZ an extension to the known ore body has been found. The extension is of large enough size and grade that a mining scheme using load-haul-damp techniques is envisaged. Since this represents a departure from the present mining scheme, questions have arisen regarding pillar sizes, room and entry sizes and possible support requirements. A task force has been set up to expeditiously plan for these things and write the necessary specifications and requirements. The fundamental question was posed to members of this group.

Jan 1, 1971

By S. Hoerger

Newmont has a large integrated operation in Northern Nevada with numerous mines, stockpiles, and processing facilities. There are over ninety defined metallurgical ore types and over sixty defined gold recovery process options. To take better advantage of the available synergies, a complete Nevada wide mine plan and process model along with a mixed Integer and Linear Programming optimization tool has been developed and implemented. This system is maintained and operated by a Nevada Planning Group. Standard in-house planning software tools and methods have been implemented at all mine sites. While increasing the effectiveness of planning in Nevada, these changes have allowed a significant reduction in overall Mine Engineering staff.

Jan 1, 1999

By N. Rowlands

The importance of mineralogical and chemical characterization of fine particles in the fields of mineral and metallurgical processing is discussed. Emphasis is placed on electron beam analysis techniques including electron diffraction and energy dispersive analysis with special reference to the scanning trans- mission electron microscope. The correct choice of instrument depending upon particle size, composition and nature of sample is stressed and the analytica1 capabilities of different types of instruments are evaluated. Recent applications of electron beam equipment to processing problems are presented and the paper concludes with a review of new developments in the fields of surface analysis and micro-diffraction.

Jan 1, 1985

By Y. C. Lo

This paper presents the development of ultrasonic grinding technology for material and mineral processing. The principles underlying this new technology, as well as their implementation in two laboratory scale devices are described in detail. Ultrasonic grinding experiment results are discussed with respect to operating variables and the achieved product sizes. Special attention has been given to the electrical energy consumption of the grinder, and an attempt to compare its efficiency with tumbling mills has been made. A mechanical system capable of measuring the specific grinding energy is also described.

Jan 1, 1991

By L. Rudolphy, P. Tähkiö

"The cPlant is a modular flotation plant which has been designed to minimize capital expenditure and risk. The plant is based on a number of standard modules, for both flotation and ancillary equipment, which can be configured to give the required flowsheet for the ore being treated. All of these modules can be rapidly deployed and erected onsite, minimizing not only engineering time and site preparation but reducing the time taken to get the plant up and generating revenue. Given the paradigm shift in flotation circuit design that has been employed in the cPlant it may allow smaller, previously uneconomic deposits to be exploited and create a more cost efficient upgrade route for existing plants. This paper introduces the cPlant and presents a case study comparing EPC cost and development timing of a cPlant against a traditional flotation circuit design. INTRODUCTION In the development of any mining project the cost associated with process plant engineering, equipment procurement and installation can affect the financial viability of a project. This is of special significance for smaller scale mining projects which perhaps don’t have the mine-life or revenue generation to justify the payback on a modern processing facility. Listening to customer feedback and understanding the challenges that small to mid-sized projects can face lead Outotec to the development of the cPlant. Modularization of mineral processing plants isn’t a new idea with a number of examples being reported in literature for gravity gold (Cabot, Trudel and Cabot, 2001; Gray et al., 2006), dense medium separation (September and Abate, 2006) and even hydrometallurgy (Saario et al., 2013). All these plants have been developed to try to improve on the traditional economics associated with fixed processing plants. Using standardized modules to construct a plant reduces engineering time and design costs which can both be beneficial to the outcome of a project. In addition the modular nature of the plant lends itself to transport to remote sites and rapid installation with only minimal site preparation required. A plant of modular design also has several other advantages over its conventional cousins. Firstly it is relatively easy to expand by duplicating existing modules. Secondly the modules can be treated as building blocks for the process and rearranged if a change in conditions requires flowsheet adjustment. Thirdly, there is potential to disassemble and remove the modular units at the end of the mine life. The ability to easily disassemble, re-pack and transport the plant to a new location not only is important to the long term environmental footprint of an operation but can also be seen as a bonus to an operator that has a number of small ore deposits. If applied in this way modular plants have the potential to create a whole new operating model for previously unviable ore deposits."

Jan 1, 2016

By Wayne J. Nordstrom, Dennis L. Murr, James E. Wennen

National Steel Pellet Company (NSPC) conducted pilot scale testing and computer simulation studies which indicates that the capacity of the secondary grinding mill could be increased and that concentrate grade improvement could be expected with improved classification in the grinding circuit. Based on these studies, a decision was made to modify one secondary ball mill line at NSPC to include both cyclone and screen classification with magnetic separation applied to the circulating load. This paper will briefly discuss the studies leading to the decision to modify the circuit, the design of the modified circuit and the initial start-up and operating experience.

Jan 1, 1997

By R. L. Grayson

Following lip on a USBM-sponsored research project, the authors have utilized the knowledge-base structure and system concepts from the Sun Sparcstation-based worker scheduling system of the Mine Management Support System to develop a PC-based application. The new software adopts the nested-window concept to facilitate data collection and modification on personnel, their availability on a shift, and work priorities for a shift as well as to allocate manpower optimally on a work shift and delineate supervisory training responsibilities. The various components of the software are described in detail, along with enhancements made to the original system.

Jan 1, 1996

By E. A. Twichell

An entirely new concept in the effective utilization of magnetic, energy has resulted in a major break-through in the design of magnetic separation equipment. One of the first applications of this concept has resulted in the development of a Permanent Magnetic Wet Drum Separator with strength .and operating characteristics equal to Electro Wet Drum Separators. Prior to this development when strength and adjustability were required, electro wet drums were specified even with all their drawbacks. The electros, by nature, are subject to coil failure or burnout, over-heating and loss of strength, high power consumption and generally high maintenance. Now the high strength and the adjustability, formerly the exclusive property of electros, has been engineered into permanent wet drum separators. These units combine maximum field strength in the separation zone with strength adjustment to suit changing conditions. Adjustment can be effected while the drum is in operation without stopping either the feed or the drum.

Jan 1, 1967

By P. A. S. Manning

Eastern Jamaica consists predominantly of non-carbonate rocks reaching elevations of over 2200 m. The area is drained by a well established river network which supplies close to 30% of the sand and gravel used by the building and construction sector. Present high extraction rates and slow rates of replenishment will result in early exhaustion of this source of aggregate. A number of volcanic and carbonate rocks are being examined as a possible source of high quality aggregate which meet the requirements for all types of construction. Preliminary evaluations show a dacitic deposit to be the most suitable source for aggregate use.

Jan 1, 1998

By Jurgen Hahn

The paper reports on both, the design and decision making for the filters in a backfill plant in Europe as well as more then 10 years of operation and maintenance experience of the vacuum disc filters installed. It begins with the first step, the filter sizing based on a sample provided by the customer, followed by the commissioning of the filter units and reports on the development of the filter performance during the following 10 years of operation. Based on the physical properties of the sample and the process targets of the client for the backfill plant, the paper shows the logic steps taken in the laboratory to ensure the target moisture, determine the required filtration area and filter size as well as the selection of the ancillary units and the formulation of the performance guarantee. The paper discusses some issues with filter operation during the commissioning phase and the actions taken. Finally, the paper concludes by highlighting the gradual change over the more than 10 years of operation and how this change affected filter performance and operating costs.

Feb 1, 2024

By P. Songfack

In this work, the slurry flow in the ball mill is solved with Navier-Stokes' equations and the marker and cell technique (MAC), which tracks the fluid-free surface. Considering different planes in the radial and axial directions, this numerical approach leads to the direct calculation of the slurry velocity profile, mill holdup, and volumetric flow in the ball charge and pool. The MAC technique takes as input, the results of a direct three-dimensional simulation of the motion of grinding media, and in turn, provides a detailed knowledge of the hydrodynamics of slurry flow through the porous structure of ball load. This technique is a new approach to the mass transport problem that overcomes the limitations of indirect studies such as residence time analysis and holdup measurements.

Jan 1, 1994

By Lisa A. Banick, Robert A. Rubin

The lawyer's role in underground construction, certainly for the past 20 years, has been principally that of the advocate in disputes resolution. Disputes in underground construction have been steadily increasing, making the lawyer a more prominent participant in the underground construction process. It is widely believed, however, that this is not a salutory state of affairs. It is our thesis that lawyers ought not be eliminated from the process, but rather that their role should be changed. They should function as prophylactics rather than as swords, i.e., they should be used to prevent or reduce disputes rather than, after the fact, to champion their clients' causes. a. Mr. Rubin is a partner in the New York law firm of Postner & Rubin. He has litigated and arbitrated numerous complex construction disputes. He has also participated in efforts to improve contracting practices on committees of ASCE and the National Academy of Engineering. b. Ms. Banick holds a BS in Civil Engineering from the University of Virginia and is a law student at New York Law School. She is a law clerk at Postner & Rubin.

Jan 1, 1983

By D. Yeager

Researchers at the U.S. Bureau of Mines have successfully used a genetic algorithm to tune computer models of three column flotation units simulating a separation circuit. The computer models rely on empirical constants that are selected so that the models accurately predict the performance characteristics of individual column flotation units. Unfortunately, these empirical constants have traditionally been selected using a time consuming trial and error process. A new and more efficient approach to selecting empirical constants for computer models has been developed. A genetic algorithm has been used to select the empirical constants for column flotation models used to simulate a three column circuit. Genetic algorithms are search algorithms based on the mechanics of natural genetics. They rapidly locate near optimum solutions in difficult search spaces. Bureau researchers have used these innovative search algorithms to dramatically reduce the time needed to select empirical constants for column flotation models. The approach is applicable to the selection of empirical constants for numerous other computer models.

Jan 1, 1995