Search Documents

By E. Stolarski

The circulating fluid bed (CFB) technology can proudly point to its history of more than a quarter of a century of commercial operations. Over 80 CFB units operate in aluminum calcining, coal combustion and gold roasting. This paper describes the invention of the circulating fluid bed and chronicles its development and evolution from calcining through coal combustion to gold roasting. It presents performance data of Lurgi's CFB units in operation and highlights the six gold roasting plants currently operating throughout the world.

Jan 1, 1998

By N. Voennann

Stillwater Mining Company operates an electric furnace at its smelter in Columbus, Montana to treat a Ni-Cu-platinum group metal concentrate along with secondary PGM bearing materials. Hatch Associates has designed several improvements to this furnace, which was originally built by others. Implementation of these relatively low cost improvements has resulted in substantial increases in furnace availability and capacity, along with reduced unit costs. ? The improvements included: ? Installation of water-cooled copper cooling elements to stabilize refractory wear and increase furnace life.- ? Improved furnace 'bindings, to enhance the furnace's structural integrity by improving the contact between the refractory and cooling elements, and by promoting tight brick joints resistant to matte or slag leaks. ? Adjustment of the electrode regulator to allow higher furnace power levels. ? Installation of an automated air-slide (aeration conveyor) feed system to evenly distribute the furnace feed in an insulating layer on the bath surface. This "black-top" practice reduces unit energy costs and makes available additional smelting capacity.- ? Electrode seals to reduce ingress of air that absorbs heat before exiting the furnace in the off-gas stream. The saved energy can be used to smelt additional concentrate. This paper describes the above furnace modifications, and the benefits derived from their implementation.

Jan 1, 1998

By L. Alan Weakly

The Powder River Basin of northeastern Wyoming and southcentral Montana contains the largest strip minable reserve of compliance coal (0.27 kg or 0.6 or less Ibs of sulfur per million Btu) in the United States. In mining parlance, it is the mother lode. Wyoming's portion of the Basin is called the Southern Powder River Basin (SPRB). It has been the nation's top coal producer for the past nine years. And based on 1997 production statistics and estimated strippable compliance coal reserves, Wyoming should remain the nation's top producer for the next 51 plus years. In August 1994, ME featured 10 articles that covered all aspects of coal production in the SPRB. In this issue, five authors update the 1994 articles and provide a pre- diction of what the Basin will look like at the turn of the century. In addition to this article, the titles and authors of the other five articles include: ? "Geology of Wyoming's Powder River Basin coal field," by Gary B. Glass and Robert M. Lyman. ? "Coal quality challenges in the Powder River Basin," by Sharon Roness, Richard A. Turpin and Robert A. Young. ? "Markets for Southern Powder River Basin coal," by , Patti J. Best and Patrick W. Wright. ? "Evolution of mining equipment in the Powder River Basin," by Kenneth R. Miller and James L. Long. ? "Hauling coal into the 21st century," by Dave Willis and Will Cunningham.

Jan 1, 1998

Since 1992 the Grasberg Mine, located in the remote regions of Indonesia, has utilized the Modular Mining System. Over the last several years, major steps have been taken to maximize this productivity enhancement system. These steps include; the Automated Lineup, the Linear Program upgrade, tracking of Mean Time Between Failure, a MEDS system interface, a VMIS system interface, and implementation of the new Graphical Operator Interface Console with Global Positioning, This application of new technology and innovation has lead to improved performance, understanding and reporting, as well as the quality of the Indonesian Engineers. These efforts have contributed 10 Grasberg achieving one of the lowest mining costs in the copper industry.

Jan 1, 1998

By B. Hearn, Malcolm J. McPhersqn

Since 1993 Inco Ltd. has been using wet shotcrete at Stobie Mine. Through an evolving process the mine has reduced the thickness and fiber content of its steel fiber reinforced (sfr) shotcrete. However, the shotcrete support is used without any other type of ground support. A process referred to as bolt less shotcrete. Boltless shotcrete is used as the primary ground support method in development headings when the sub level caving front passes through the development drifts which now serve as migrating ore draw points. Although there are references of drifts and tunnels supported by shortcrete only, written accounts are rare. The empirical nature of most underground support designs makes them of limited value in a boltless environment. Considerable amounts of material testing and insitu trials have been completed in order to estimate material property strengths. Material testing, for adhesion, flexural strengths and compressive strength along with observational insitu data have been used to evaluate the performance of shotcrete. Punch tests on panels have also been undertaken in order to gain insights on the limitations of the two dimensional testing common to the laboratory. All these design aspects have been successfully utilized to design an efficient ground support process.

Jan 1, 1998

By P. K. Sollars, M. A. Alspaugh

In May of 1996, Twentymile Coal Co. began Longwall mining in the Foidel Creek Mine's East Mine District. These Longwall panels are some of the longest in the world (5.48 km/18,000 ft) with very difficult and challenging geometry. The conveyance system is 1,800 mm (72 in) wide, has a 4,500 mtph (5,000 stph) capacity and employs multiple tripper drives. The trippers include traditional powering designs as well as unique regeneration and braking designs. Several components were developed specifically for this application including a mobile tail brake. Control algorithms were carefully developed and tested via computer modeling. A world production record was achieved in the third month of operation and over 1 million tons were mined in June 1997.

Jan 1, 1998

By James J. Gusek

The Atlantic City iron mine is located in Fremont County in central Wyoming, near the historic gold mining camps of Atlantic City and South Pass City. The mine lies on the southeast flank of the Wind River Mountains at an elevation of about 2,470 m (8,100 ft) above sea level (Fig. 1). An 81-h M2 (200-acre) tailings impoundment at the Atlantic City taconite operation has been a source of blowing dust. The site qualified for reclamation under Wyoming&apos;s Abandoned Mine Land (AML) reclamation program. The ultimate reclamation construction incorporated commercially available organic amendments and fertilizers into a 300-mm- (12-in.-) thick cap of a sterile clay loam cover material. The water level was lowered in an adjacent flooded mine pit that was feeding uncontrolled seeps into the tailings basin. A wide tailings pond spillway was built that allows flood control while minimizing seasonal water-level fluctuations in the pond. Rock berms and rock snow fences were built for wind-erosion control and soil-moisture preservation. Future work includes tree planting in the protective wind/ snow shadows of rock berms and rock snow fences and plugging a decant pipe. US Steel opened the Atlantic City iron mine in August 1962. It closed in 1983. Taconite iron ore was mined by surface methods. The ore was magnetically separated from the waste. The magnetic concentrate was mixed with bentonite, formed into pellets and roasted to produce a blast furnace feed stock for US Steel&apos;s blast furnaces in Geneva, UT. The pellets were hauled by rail to the Geneva Iron Works. The Atlantic City Mine produced three types of wastes. These included waste rock overburden from mining, a coarse-grained (sand to small-gravel sized), nonmagnetic reject rock termed "cobbs" and fine-grained tailings ranging from 600 to 75 µm (28 to <200 mesh). The waste rock has been used as an aggregate/rip rap source by a local contractor and the Wyoming Department of Transportation (WYDOT). WYDOT also

Jan 1, 1998

By D. A. Bird

Water chemistry data were used to identify the sources of ground-water and surface-water inflow to the IOZ block cave mine. Water samples were collected to obtain vertical and lateral hydrochemical profiles within different levels of the underground workings. Water chemistry data were evaluated in conjunction with geologic and structural information to define controls on locations of ground-water inflows, and to select targets for drilling and interception of water. Drilling has intercepted water-producing zones that were previously unidentified through mapping and drilling. The program has resulted in a reduction in water inflows to the block cave area.

Jan 1, 1998

By D. W. Lawler

Prior to the manufacture of sulphuric acid in metallurgical plants, the SO2 rich gas from the smelter, roaster, or furnace must be cleaned to removed particulates, volatile contaminants, SO3, and water. Cleaning is accomplished by contacting the. gas with cooled weak acid. The system is designed so that all the contaminants, originally in the gas are captured in the weak acid, which then becomes an effluent from the plant. Historically, the entire weak acid effluent stream has been treated for disposal, with no attempt to recycle or recover any part if it. This is becoming increasingly environmentally unacceptable, and operators must consider better methods of treatment and recovery. In this paper, Kvaerner Chemetics discuss a number of options that allow the contaminants to &apos;be separated from the acid&apos; value. This will result in an acid byproduct that can be sold or used elsewhere, and will minimize the volume of hazardous byproducts that must be discharged.

Jan 1, 1998

By John Marsden, John Mansanti, Jim Arnold, Mike Gleason

DOUG HALBE: We&apos;re not quite to the end of our session, but we&apos;re close. We&apos;ve had a lot of fun with some of these spill ideas. But these are serious problems, and I think we might be able to benefit by continuing to compile these. Several years ago, the metallurgists at the various operations of Gold Fields Mining Company had a newsletter that came out every two months for several years. This publication consisted of short articles by the staff at the various operations, plus a few others, on problems they&apos;d had and how they solved them. One very useful article, "Things We&apos;d Have Done Differently at Chimney Creek," was written shortly after start-up. John Marsden was the editor and John Mansanti contributed to it, as did Jim Arnold (our distinguished co-chair) and Mike Gleason. I would be interested, with the permission of the audience, in editing that article to make it a little bit less abrasive and putting it into the record here. I think it&apos;s a useful SME function to maintain a list of things we&apos;ve done wrong in plant design, things we don&apos;t want to do again. If we have another open session in the future, would others be willing, even anonymously, to contribute, bring slides, and say "Hey, look at the goofs we made?" [laughter, followed by support from the audience] Okay, we&apos;ll plan on that. And we&apos;ll try to include the Chimney Creek list in the transcript of this session-perhaps edited a bit.

Jan 1, 1998

By R. L. Kloberdanz

Peruvian legislation requires the preparation of an Environmental Impact Study (EIS) for new and expanding mines/beneficiation facilities and the preparation and implementation of an Environmental Adjustment and Management Program (PAMA) to control and mitigate environmental impacts associated with existing mining/beneficiation activities. Shepherd Miller, Inc., developed guidance documents for preparing an EIS and PAMA for Peru&apos;s Ministry of Energy and Mines and presented workshops to Peru&apos;s mining industry on preparing an EIS and PAMA. This paper discusses the process and approach taken and the results.

Jan 1, 1998

By J. A. Ehler

Speed and torque control of standard A.C. induction motors can be accomplished using a variety of devices ranging from mechanical, hydraulic, and electrical. Also, the motor can be specified as an A.C. wound rotor or D.C. motor using the associated controls. Normally, any one of these drive types can be adequately used to provide the torque control necessary to accelerate a conveyor belt system. The selection will depend on the economics, experience, and preference of the designer or end user. These drive types will be presented from a functional and performance viewpoint to assist in the understanding of the available technology.

Jan 1, 1998

By Jerry Williams

GEORGE WEINMAN: At this time, our co-chair, Jamie Davis from Phelps Dodge, will come to the podium. JAMIE DAVIS: Our next speaker is Jerry Williams from Phelps Dodge, Morenci. Jerry is the maintenance planning supervisor and is in charge of preventative maintenance and maintenance scheduling. Jerry&apos;s group uses predictive tools to monitor and predict the equipment failure throughout the mine, from pumps to shovels to motors, you name it. The title of Jerry&apos;s talk is "If You&apos;re Not Using Predictive Tools, You&apos;re Behind the Curve." I’ll turn it over to Jerry.

Jan 1, 1998

By Donald R. East

There has been an increasing trend in recent months by regulatory agencies to require that estimates be made of the hydraulic head acting, under operational conditions, on the surface of primary leach pad liners. This move towards inferred performance standards, rather than specifying a prescriptive standard for all sites regardless of economics, is to be generally welcomed. The theory of flow on a sloped beach pad, which was developed by East et al, 1987 (Reference 1 and 3) has been refined and extended. Unitized curves have been developed by graphically displaying the seepage losses and resulting dissolved gold lost as seepage through the primary liner as an aid to pad liner selection and design. Very little information is available of actual hydraulic head profiles acting on the liners beneath heap leached ores. Attempts have been made to measure these by drilling from the top of the heap and installing piezometers at the base. With this procedure it is difficult to obtain accurate data due to the fact that the drilling operation itself creates a highly permeable vertical flow path which may not exist to the same degree elsewhere in the heap. Combined with the fact that it is almost impossible to ensure that the piezometer tip is sitting directly above the liner without the risk of causing some damage to the liner itself. The best time to install hydraulic head monitoring devices on the pad liner is during construction and when piezometers can be carefully placed directly above the liner and suitably protected hydraulic lines laid to ensure full hydrostatic head measurement with simple manometer devices.

Jan 1, 1998

By Thomas J. DeMull

Amax Gold's Sleeper Mine was brought to production as an open pit mining, cyanidation milling operation in March 1986. The Sleeper deposit is unique in that it contains zones of very high grade gold ore. Despite blending of ore, mill head grades have varied over a broad range. These grade variations were anticipated during mill design and affected, in particular, the sizing and selection of equipment for the CIP circuit. When grades proved to be even higher than anticipated, design operating parameters were adjusted shortly after start-up to accommodate the higher grades. Operating results have been excellent: during the first 18 months of operations the Sleeper mill has processed 375,600 tons of ore and produced 229,000 ounces of gold.

Jan 1, 1998

By Donald D. Gullickson

The entire system is built around pre-designed and pre-engineered modules which are assembled to meet the metallurgical and production parameters of the project. The carbon vessels are the key to the flexibility of the system. The vessels are made of a coated mild steel, which allows the carbon vessels to be used in the adsorption, desorption and acid wash cycles. In the adsorption mode, the solution is pumped up-flow through four (4) vessels in series at 250 gpm fluidizing the carbon bed. When the carbon in the lead vessel is loaded, it is disconnected from the adsorption circuit via rubber hoses with quick-disconnect fittings. The second vessel is then made the lead vessel and a stripped carbon vessel is added to the end of the adsorption circuit.

Jan 1, 1998

By J. E. Wennen

Screens serve several important functions in CIL and CIP processes for gold extraction. One important screen application known as interstage screening allows slurry to be continuously transfered through a series of CIL or CIP tanks while retaining activated carbon in the tank. In some cases, this has been accomplished by using airlifts to carry slurry containing activated carbon to an external screen which separates carbon as oversize and returns it to the tank by gravity. The undersize slurry advances to the subsequent tank. More recently this has been accomplished using launder screens and Kambalda type screens. These are essentially static screens that rely on air blasts or mechanical sweepers to clear carbon away from the screen surfaces.

Jan 1, 1998

By David J. Collins

The emergence of activated charcoal adsorption as the most popular recovery method for precious metals, has led to numerous innovations aimed at increasing the efficiency of the process. This article describes a change in traditional charcoal transfer methods which will aid in reducing charcoal attrition losses. Studies have shown that significant charcoal attrition takes place during transfer, be it when using airlifts or centrifugal pumps. Tests conducted at Pinson Mines indicated a 4 to 8% loss to the minus 20 mesh fraction of charcoal after three (3) hours of pumping charcoal. Tests conducted while the author was at Jerritt Canyon indicated that charcoal transfer was a major contributor to charcoal losses; a decrease in the amount of coarse charcoal (plus 12 mesh) and an increase in the amount of finer charcoal (minus 16 plus 20 mesh) was noted as charcoal was moved to the head of the adsorption circuit.

Jan 1, 1998

By John Litz

The term "refractory gold ores" refers to a wide number of ore types which are not readily amenable to direct cyanidation. A number of processes have been used commercially, and a number of others have been proposed and in many cases pilot tested. The selection of the appropriate process for an ore should not be arbitrary. Ore grade may preclude some processes, but a good understanding of the ore mineralogy can guide the selection. Many present gold operations and many potential gold operations have faced or are facing problems with refractory gold mineralization. We at Hazen Research have had the opportunity to perform bench testwork and in some cases, pilot plant testing on a number of refractory ores. The data included in this paper are excerpted from the testing of fifteen ores which cover a wide range of mineralogical compositions. This paper is not intended to be a treatise on the processing of refractory gold ores. In many of these gold projects, not all of the standard process alternatives were evaluated, nor was adequate mineralogical work performed. Such is the dilemma of contract research. "If I believe that I don't need it, why should I pay to have it done." The intent of this presentation, therefore, is to show how different ores respond to the various processes, and to demonstrate that one must have an open mind when developing a process for a specific refractory gold ore.

Jan 1, 1998

By Ray Soper

Important progress has been made in developing the K-Process as an alternative to cyanide as a method of recovering gold from ores and other materials.

Jan 1, 1998