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By K L. Brown, J L. Mauk

Sulfide-rich scale occurs in steam and water lines at the Ohaaki geothennal field,Taupo Volcanic Zone, New Zealand. Precious metals show very high concentrations around areas ofpressure reduction (Au 15500 ppm, Ag 68800 ppm). Pyrrhotite dominates at the orifice plate due to low PH2s1PH2 conditions. Sulfide mineralogy in the scales is consistent with alteration mineralogy of the reservoir rocks. Separated steam then produces a mainly pyrite/magnetite mineralogy, with lesser chalcopyrite, where textures reflect high flow rates and high levels of supersaturation. This study outlines the effect that pressure and subsequent temperature decreases have on the mineralogy, chemistry and textures of sulfide scales.

Jan 1, 1998

By Robert Martin, Brian W. Stump, David P. Anderson

2We use field measurements to quantify physical processes that accompany different types of mining explosions. The data sets collected include three-component ground motion, acoustic, video and high speed film, three dimensional topography, geological and geophysical properties, design blast pattern and timing, and velocity of detonation in the explosive for individual borehole detonation times. The explosions include simple single-fired contained explosions, ones designed to bulk and fracture material and those that cast material. Our goal is a physical understanding of these sources for the purposes of optimizing blasting practices.

Jan 1, 1998

By J. T. YIi-Penttiia

Dust formation and reaction mechanisms of copper matte particles were investigated in simulated flash oxidation conditions. The granulated and ground matte consisted of 72 wt% Cu, 4 wt% Fe and 21 wt% S. Experiments were conducted by using a laminar-flow furnace with a reaction gas composition ranging from 20 vol% to 75 vol% O2 in nitrogen. The particle feeding was carried out by the single-particle method and samples were quenched after a specified reaction time (approximately 0.05-004 s) in a cold water film. Experimental temperatures were between 800 and 1300°C. Chemical analysis was used to determine oxidation degree, and an optical and scanning electron microscope combined with energy dispersive analysis was used for characterization of the reacted particles.

Jan 1, 1998

By Laros T, Schoenbrunn F

Deep paste thickeners have been proven capable of consistently producing medium to low slump material for disposal without the need for filters. However, proper design of the entire system is critical for a paste project to he successful. Some of the factors that must be carefully considered in design of a paste system include thickener sizing, tailings inipoundineni design, underflow pumping, and control system.

Jan 1, 1998

By B. K. Slone

The depth at which it becomes more economical to use slope access as opposed to box-cut access for near-surface coal reserves, termed "transition depth," can be established for a given coal property by considering cost estimates for those parameters that determine respective access method. Fourteen parameters that influence access cost were identified and ranges determined. A Transition Depth Formula was developed to permit determination of the better method of accessing a reserve, given such information as highwall slope, road width, total bench width, pit dimensions, road grade, belt component costs, pumping costs, and cost of overburden removal and reclamation. In most cases, in Appalachia, studies indicate that the transition depth ranges between 20 and 30 m.

Jan 1, 1998

The Waste Isolation Pilot Plant (WIPP) is adding a third fan to operate in parallel with, and supplement, its two existing main fans. An engineering analysis conducted in 1995 identified the need for improved system availability and efficiency. The WIPP, located near Carlsbad, New Mexico, is a U.S. Department of Energy (DOE) Carlsbad Area Office facility designed to permanently dispose of U.S. defense-generated transuranic waste in a deep bedded salt deposit. Engineers at the WIPP performed a feasibility analysis for either modifying, supplementing, or replacing its two main mine fans. Since the centrifugal fans were installed in 1988, multiple operational and performance concerns have been identified. A comprehensive engineering study was conducted (K. McDaniel, et al., 1997) to: identify and quantify operational concerns, evaluate possible alternatives, and recommend an optimum solution. The study indicated that adding a third single-duty centrifugal fan similar to the two existing fans, and equipping that fan with Inlet Van Controls (IVCs) was the best choice. This alternative provided the most desirable combination of operational readiness, and improving system performance. The fan installation project accommodates several operational and scheduling constraints. WIPP is scheduled to receive waste in May 1998. This milestone is proceeded by an operational readiness review. Fan installation could not be allowed to compromise the WIPP's ability to declare facility readiness and had to minimize operational disruptions during the system tie-in. All engineering for the project is completed and physical modifications started in July 1997. The project will be completed in early 1998.

Jan 1, 1998

By Leonard Harris

Good morning ladies and gentlemen. I would like to thank Hans von Michaelis for inviting me here today to talk to you on the subject of "How to Reduce Capital and Operating Costs at Heap Leaching Projects". The comments I have to offer are based on my experiences in gold heap leaching by Newmont Gold Company in Nevada, by Newcrest in Western Australia (formerly Newmont Australia), by Minera Yanacocha in Peru, by Penmont in Mexico, by Z­Mont in Uzbekistan, by the Hochschild Group in Peru and expe­riences in copper heap leaching by Magma Copper Company in Arizona and as a consultant on several other smaller projects worldwide. These comments are a mixture of technology, ideology, philos­ophy, strategy, logic and opinions and might be looked at by many of you as "one man's view". I like to look at them as "a view from the bridge". Let me add that it doesn't bother me that you may not agree with my comments and that I would be interested in your comments or criticisms at the end of this presentation. I don't intend to discuss the details of the mineralogical and metallurgical test work. I will assume, for this talk, that the test work has been conducted very carefully and that the ore in ques­tion has been determined to be heap or dump leachable. Let's begin with a couple of don'ts! ! First, "don't build the mill until you have a mine". This might sound to many of you as fundamental but believe me it continues to happen. The minable reserves should be well known and established as being economical to mine and leach. NPVs, ROis and IRRs are fine if you can be sure of the gold price you use in your calculations. The best method is to carefully estimate the capital cost and, most importantly, the operating cost per ounce of gold recovered which should include the repayment of the borrowed capital and the interest thereon. For example, if the operating cost under these conditions is $200 per ounce, you have a project. If it is $400 per ounce, walk away f om it. Incidentally, the same prin­ciple can be applied to projects involving other metals such as silver, copper, lead, zinc, etc. The second don't is - "don't be sheep". Don't climb on the bandwagon with respect to design and operation because every­one else does it a certain way. Keep an open mind, be versatile, look for change, look for every possible innovation for reducing capital and operating costs. Beware of those who will tell you "we tried that it won't work" or "it's too expensive" or "that's a crazy idea" , <' ''what do you know about mining - you are a metallurgist aren't you" or "what do you know about metallurgy - you are a miner aren't you" or "only geologists can handle this issue". Be careful about pigeon-holing people according to their basic degree and experience. In these days of low metal prices, we need to consider everybody's ideas, as crazy as some of them might seem.

Jan 1, 1998

By Thomas J. DeMull

Heap leaching was introduced to the precious metals mining industry approximately two decades ago as a simple, low cost method for recovering gold and silver from ores. Since that time, operational experience has contributed to knowledge and understanding of the process, making it a reliable alternative to conventional milling processes for low grade ores. At time of this writing, dozens of heap leach operations are active producing hundreds of thousands of ounces of gold and millions of ounces of silver annually. These successes have caused the popular press to acclaim heap leaching "high-tech" gold mining, but, despite the hype, the process remains a simple one. An example of simplicity in heap leaching is the operation established in 1986 at Amax Gold's Sleeper Mine. Starting with a simple goal, namely to produce gold from sub-mill grade ore at low cost, heap leaching was rapidly implemented at Sleeper; only five months after testwork started, leaching commenced on the first commercial scale, 50,000 ton heap of low grade ore. Sized at 600,000 tons per year to produce 10,500 oz gold per year, the low grade heap operation has performed beyond expectations. During the first year of production, 881,800 tons have been leached producing 15,665 oz of gold and 35,528 oz of silver. Operating ·costs for the first year have averaged $112 per oz gold produced ( or $95 per oz if silver credit is included). Successful implementation of heap leaching at Sleeper has had a dramatic impact on ore reserves and future operations.

Jan 1, 1998

By Rick T. Richins

Despite what may be overwhelming evidence that natural degradation of cyanide and cyanide attenuation in hydrogeochemical processes are capable of reducing or eliminating potential water quality problems associated with heap leach facilities, the recent sharp increase in the price of gold and wide interest in the cyanidation process has focused all regulatory eyes on cyanide leaching. Regulations continue to increase, design criteria are more strict, and detoxification requirements approach or exceed the level of detectability. Current governmental regulation of mining and milling operations using cyanide varies considerably from state to state. The lack of regulatory consistency at this level is largely attributable to the current Bevill Amendment exclusion of mine wastes as potentially hazardous wastes, the undefined status of the Environmental Protection Agency's ongoing mine wast study effort, and the mining industry's reluctance to develop a consistent policy regarding state versus federal mine waste regulation.

Jan 1, 1998

By R. L. Zick

The High Density Sludge Process was originally developed by Bethlehem Steel Corporation for use on acid mine drainage and diluted waste pickle liquor discharges requiring continuous chemical treatment systems. This work began in the early 1970s and was first put into practical use around 1973. To date there are approximately 15 operating systems which have been installed on mine drainage in the United States, and another 10 systems worldwide. Dense Sludge is an innovative and improved method for treating acidic metal bearing streams in a manner which minimizes the volumetric generation of sludge for disposal. The technology utilizes a sludge recycle process which forms particles that have a low affinity for water, unlike conventional metal hydroxide solids which contain tightly bound interstitial waters. Typical acid mine drainage streams contain high sulfate concentrations which combine with calcium ions in lime based treatment systems to form gypsum crystals. The physical form of this gypsum is radically altered when the Dense Sludge process is utilized compared to the form generated in conventional lime treatment systems. The characteristics of the metals particles are also changed in this process, as the metal hydroxides are converted to metal oxides. Slides No. 1 and No.2 show scanning electron micrographs of conventional and densified sludges illustrating these differences. The magnification used was 300X. The dense sludge particles settle faster, dewater more readily, are more easily pumped, and hold much less water than conventional precipitates. In some cases, because the metal content of the sludge is more concentrated, it can be economically recovered.

Jan 1, 1998

Since it was first introduced, the Coal Mine Roof Rating (CMRR) has been widely accepted as a tool for geologic characterization and mine planning. This paper discusses the application of the CMRR to another practical ground control problem. Extended cuts (cuts greater than 6 m (20 ft) in length) are commonly used with remote control continuous miners. Extended cuts can greatly increase productivity, but they have been associated with a number of fatal roof fall accidents. When extended cuts are attempted in weak roof, the roof may collapse before it can be bolted, causing hazardous conditions. Until now, it has not been possible to predict where conditions may not be suitable for extended cuts. In this study, data on the CMRR and extended cut experience were collected at 36 mines in 7 states. It was found that when the CMRR was greater than 55, deep cuts were routine in nearly every case. When the CMRR was less than 37, extended cuts were almost never taken. Between 38 and 55, extended cuts were feasible sometimes but not others. The data also shows that extended cuts are less likely to be stable if either the entry span or the depth of cover increases.

Jan 1, 1998

Jan 1, 1998

By Chappell B

Backfill in the form of mine waste tailings has inherent problems associated with attaining adequate strengths upon placement. Fines are usually removed to ensure adequate drainage, which lowers the cohesive strength of the fill, leaving the fines to he placed in a tailings darn. Electro-drainage and electro-chemical grouting is examined to investigate its effects on densification and shear strength within a silty clay tailing having low permeability and shear strength. Two separate grouting mechanisms are observed for the iron and silica grouts used. Electro- osmosis is associated with iron grout that deposits within the tailing matrix under a converging pH gradient, and increases the permeability of the tailing. This process initiates cation exchange and causes cementing of the granular contact points between the clays. Electro-phoresis causes sodium silicate solution to deposit silica grout in the voids of the tailings. The resultant effect of these mechanisms results in an increase in cohesion, leaving the void ratio of the iron grouted tailings as it was but significantly reducing the void ratio of the silica grouted tailings.

Jan 1, 1998

By Chend J

Research conducted into backfill drainage at Mount Isa Mines since 1992 is described. Piping in draining backfilled scopes has been the primary cause of bulkhead failures and emphasis is placed on research into the piping mechanism. Laboratory and in situ tests aimed at understanding the piping mechanism have been conducted and the results are presented. A case history of piping in a draining bench scope fill mass is described and a technique for reducing the potential for bulkhead failures in hench stopes is presented. Hydraulic fill is produced by standard cycloning of tailings and the overflow (reject material) is sent to thickeners prior to placement in the tailings dams. Research into the partial introduction of thickener underflow into the backfill system and its influence on backfill drainage is also descrihed.

Jan 1, 1998

By E. A. Metz

Silicon dioxide, silica, is the most common oxide in the earth&apos; s crust. The health effects of silicon dioxide dust have been known since Biblical times. Agricola&apos;s book, published in the mid 1500&apos;s on occupational medicine, described a lung disease that afflicted miners. He observed a disease in miners that caused shortness of breath, coughing and wasting. Add fever, chest pains and fatigue and we have the current symptom complex of silicosis. As we approached the 21stcentury, the Labor Department began an aggressive campaign to combat silicosis-a preventable disease. Unfortunately, many publications do not clearly differentiate the polymorphs of silica known to mineralogists. Crystalline silica, i.e., alpha quartz, tridymite and cristobalite need to be considered differently from the amorphous forms of silica. Freshly fractured surfaces of the silica and host specific responses will be examined. Recent research focuses on the biologic interactions of free radicals generated by mineral particles. This results in cell injury and DNA damage, in turn leading to fibrogenesis and possibly carcinogenesis. In addition to particle-cell interactions, emphasis is given to lung defense mechanisms.

Jan 1, 1998

By P. G. Kovalchik

Recent research conducted by NIOSH, Pittsburgh Research Laboratory showed that electrical current levels permitted under present regulations may not limit cable temperatures to less than 90°C in reeled trailing cables. Reeled cables, tightly wrapped with many turns, all carrying current in an enclosed space, can become overheated due to poor heat transfer. This overheating can cause the cable insulation to soften and become easily damaged. The damaged insulation reduces the life of the cable and can lead to shock, electrocution, and mine fires. This paper describes a method of measuring the conductor temperature of mine trailing cables during normal operation. The temperature is measured using a 50/125 micrometer Graded Index Multimode Optical Fiber located in the center of the metallic conductors. Distributed temperature measurements are made using an Optical Time Domain Reflectometer (OTDR). This system is capable of measuring temperature with an accuracy of plus or minus one degree centigrade over a length of 4 km at 1-m intervals. With this unique way of measuring temperature, tests can be conducted simulating actual mine conditions and provide important data to allow MSHA&apos;s Approval and Certification Center to develop approval criteria for cyclically rated reeled machines.

Jan 1, 1998

By Gunther F. Leichtle, James A. Finch, Colin A. Hardie, Cesar O. Gomez

"The recycling of wastepaper has become an important and common process worldwide. Techniques similar to those used in the mineral processing industry are used to produce high quality recycled fibers for use in newsprint. The mineral processing group at McGill University in conjunction with the Pulp and Paper industry (Mechanical and Chemi-mechanical Wood Pulp Network) has adapted one of these techniques, column flotation, for the purpose of deinking wastepaper. This article describes the typical process of recycling wastepaper from a mineral processing point of view. It also presents results from McGill University's flotation column test work at a Quebec wastepaper recycling facility.IntroductionThe recycling of wastepaper has become an important and common process worldwide, including Canada which is now the world's largest importer of wastepaper (CPPA, 1996). Much of the current drive to increase the utilization rate of recovered paper is a reaction to the solid-waste disposal problem that faces many Canadian and U.S. municipalities. The real problem in the disposal of solid waste is not the absolute amount of garbage that must be disposed of each year but this amount in relation to available disposal capacity.Environmental restrictions on the creation of new landfill sites and incinerators (the two main options for disposal of municipal solid waste) have tightened the demand/supply balance in the solid waste disposal market. This shrinking availability of waste disposal sites in the face of increasing population with greater disposal requirements defines the Developed World's solid waste crisis. Not only are there fewer disposal sites available, but the costs of using them is skyrocketing. These factors have increased government regulations mandating recycled paper content in newsprint. Conservation and environmental issues make the current drive for wastepaper recycling a real issue and business opportunity.A key to the success of producing quality recycled fibers from wastepaper is the deinking technology. The production of tissue papers, paper towels and newsprint requires regenerated fibers which are substantially free of ink particles. Of the various options available, mineral processing techniques can offer the most economical, environmentally acceptable and versatile strategies (Yoon, 1993). Today, it is recognized that flotation is one of the most effective processes for removing ink particles in the production of a high quality product. In a collaborative program with the Pulp and Paper industry, the mineral processing group at McGill University has adapted column flotation technology for this purpose. This article will describe the typical process of deinking from a mineral processing point of view (Part A). It will also present some results from McGill University's flotation column test work at a nearby paper recycling facility (Part 8)."

Jan 1, 1998

By M. R. Yenchek

Faulty insulators on mine trolley/track haulageways may allow the flow of leakage currents into the mine roof and ultimately result in combustion of the local roof material. The National Institute for Occupational Safety and Health (NIOSH), Pittsburgh Research Laboratory (PRL), has devised a passive means to detect overheating insulators on direct current systems. The detector consists of a spring-loaded cartridge that ejects a reflective streamer of white Teflon tape when subjected to elevated temperatures. The cartridge assembly can be easily installed over the outer metallic shell of an existing trolley line insulator. If an insulator overheats due to ground leakage currents, the visible streamer alerts mine personnel traveling on the haulageway.

Jan 1, 1998

By M. T. Errington, P. C. Miller, W. E. Hardwick

Paper discusses in general terms the techno economic merits of various types of aerated biological reaction systems. The current status of the technology leaves many questions unanswered and hence the choice of the best system to employ is open to discussion. Reasons are given for the choice of the reactor system to be built and operated by Davy McKee. The pilot plant has been designed to provide answers to a number of the questions posed by this technology.

Jan 1, 1998

By P. Ollivier

The ore-processing plant of the Soremib mine Pour a (Burkina Faso) has now been in uninterrupted operation for 3 years. Ores from the oxidized and non-oxidized zones of the deposit are processed together in one flotation unit. About 60% of the gold is free and is recovered in a gravity processing unit. The residual gold in the flotation concentrate is processed on the spot by cyanidation and carbon-in-pulp.

Jan 1, 1998