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By Ann M. Hagni

Microscopic and sub-microscopic gold commonly occurs in the sulfides pyrite (FeS2) and arsenopyrite (FeAsS). To recover refractory gold from pyrite and arsenopyrite, these sulfides are roasted to create porosity and permeability prior to cyanide leaching. A new technique of adding Ca(OH)2 and roasting. lime roasting. is being tested for retention of contaminant sulfur and arsenic and effectiveness of gold extraction. The lime roasting of pyrite at 500°C contains anhydrite (CaS04). oldhamite (CaS). calcium sulfite (CaS03). hematite (Fe2O:J), magnetite (Fe304). and minor amounts of pyrrhotite (Fe1.xS) and pyrite. At 600°C. 650°C and 700°C. the main constituents are anhydrite. oldhamite. and hematite. At 750°C. 800°C. and 850°C. anhydrite and hematite are the predominant phases with minor oldhamite. The roasted arsenopyrite at 450°C contains arsenic sulfides. calcium sulfite. hematite. and minor oldhamite. magnetite. and pyrrhotite. At 650°C. 700°C, 750°C. and 800°C, anhydrite, oldhamite. arsenic sulfides, and hematite are present. At 850°C. the same minerals are present with only minor oldhamite. The textures indicate excellent porosity and permeability at high temperatures. At lower temperatures, rims of low porosity and permeability surround many of the pyrite and arsenopyrite particles, and the complete oxidation process from pyrite to pyrrhotite to magnetite to hematite can be observed in individual particles. Additional process mineralogy techniques employed in this study are electron spectroscopy for chemical analysis (ESCA) and cathodoluminescence microscopy (CIM) in the determination of the calcium-sulfur-oxygen phases. Automated scanning electron microscopy-energy dispersive spectroscopy was utilized to analyze particles for gold content. Reflected light microscopy (RIM) revealed arsenopyrite and pyrite encapsulated in quartz particles of the gold-bearing concentrate, gold roast calcine, and cyanide leach residue.

Jan 1, 1991

By O. A. Bascur

The problem of setting the proper control objectives and/or having several objectives to be met in the implementation of grinding control strategies can be resolved. The design and implementation of a distributed control system for safe operation of a grinding circuit while maximizing profit is presented. An optimal recovery through- put target for a desired grind is accomplished by advanced control strategies at the DCS level. A mill load constraint control technique provides stable operation with a substantial increase in throughput, while the desired grind index is maintained by an inferential grind control technique without using a particle size analyzer. The integration of crushing/grinding and flotation in the overall design was the key to the success of the project. This synergistic effect was obtained by implementing a computer plant management system in the concentrator. The overall/philosophy was to keep the implementation simple while using new technology creatively.

Jan 1, 1991

By Granholm S

The current emphasis within the mining industry to reduce the cost of production has stimulated interest in the fields of maintenance and operational reliability of capital intensive mining equipment. From an economic point of view, high reliability is desirable to reduce the maintenance costs of the systems. Two graphical methods consider reliability analysis. The first one, the method of Total Time on Test (177)-plotting deals with the reliability data which are free from trend and serial correlation. The second method which is based on time dependent modelling approach deals with the data which are not free from trends and serial correlation. The examples show how these graphical methods can be used to calculate the optimal maintenance intervals for components or systems.

Jan 1, 1991

By Mario Giavani

"IntroductionBy the 1980s, the continuous casting process had almost replaced the ingot casting of steel in Japan, Europe and North America. While economic benefits were probably initially the prime motivator, the transition rapidly proved that continuous casting in conjunction with ladle metallurgy offered a much greater degree of process control and made possible routine steel specifications not previously available.This new technology demanded improved procedures for the quantitative addition of the required metallurgical reagents, especially as regards the more volatile or toxic elements such as calcium , boron, carbon, sulphur, lead and tellurium. The injection of a thin steel tube containing the additive into the metal bath of a ladle refining station offers the best procedure for this. In the industry this has been referred to as ""Cored Wire "".Operators using this technology find that they are faced with balancing the injection speed against the small cross section of the tube to feed the required amount of reagent within the short time span available to the operation. Large-ladle shops requiring major quantities usually resort to multiple machines and high speeds. Many machines approach a maximum feed rate of 400 m/min. Higher speeds exceed the melting rate of the system, and the ferro static buoyancy of the tube will cause it to coil up the ladle wall and possibly resurface into the slag layer, and even eject itself above the surface. Under these conditions, exact control of element recovery becomes difficult, especially with the commonest addition, calcium silicon alloy.Many experts are persuaded that the final melting position of the carrier tube has major importance in establishing consistent element yield to the bath.For instance, the vapour pressure of calcium at l500 °C is close to I bar. Reaching a melting depth sufficient to accommodate this value is considered to be critical to achieving an acceptable and reproducible yield.Many studies have elaborated semi-empirical formulae to establish the melt zone depth, connecting this value essentially to the diameter of the tube , the injection rate and the superheat of the steel. The author's experience in steelmaking could not confirm such formulae in many cases, and he set about to develop a mathematical model which would be useful in addressing this problem, taking into account the several parameters which will regulate the behaviour of a filled tube immersed in molten steel."

Jan 1, 1991

By Stefan K. Schwank

The paper describes the two foundation techniques - mini piles and postgrouted bored piles. The mini pile system is presented with its design and installation parameters, especially the drilling technique. Two case histories demonstrate the application under extremely limited space and traffic conditions and the required modifications of the equipment. After the description of the postgrouted bored piles and its grouting technique, the paper gives a comparison of postgrouted piles and standard piles on a large basic test in Germany. The Brooklyn Queen's Expressway, N.Y., case history shows the application of this technique after redesign of the original proposal. 1. General Increasing requirements to improve existing foundations to carry additional loads and to increase the bearing capacity of bored piles leads to two new piling techniques: the mini-pile and the post grouted bored pile.

Jan 1, 1991

By W. E. Foreman, A. Hayatdavoudi, A. Ghalambor

The objective of this investigation was to determine the sensitivity of three selected input parameters in the operational control of continuous bottom fed thickeners used for the treatment of coal refuse slurries. The three variable parameters were "Feed Flow Rate," "Feed pH," and "Feed Solids Concentration." These three input parameters were studied under three cationic-anionic polymeric conditions. For each polymeric condition, two mathematical models were developed, one for overflow response and the other for underflow response. The combination polymers produced the best quality of overflow and underflow. For this polymeric condition, change in the feed solids concentration was the most sensitive factor in the maintenance of the overflow quality, and the feed pH was the most sensitive factor for the maintenance of underflow quality. The mathematical models generated a set of plots that would allow an operator to control and/or adjust any of the three variables to achieve optimum conditions.

Jan 1, 1991

By D. M. Hausen

The role of applied mineralogy in mineral beneficiation begins with early prospect evaluation, and continues through stages of amenability testwork and pilot plant studies to the ultimate development of viable processes for mineable orebodies. After plant construction, mineral products from various locations, i.e., grinding circuits, flotation cells, gravity circuits, kilns, smelters, etc., require quick identification and control monitoring for optimum efficiency and recovery. Ore/gangue minerals are identified, quantified, and textural associations investigated by microscopic, spectrographic, and electron-optical instruments. Mineralogic analyses of large numbers of samples have required the development of sophisticated computer systems that merge analytical and mineralogic data into useful diagnostic data bases

Jan 1, 1991

By R. H. Crist

Reactive components of algal cell walls include uronic and alginic acids: In addition, many marine species have half ester sulfate groups which function as fixed anions. Associated metals vary with the media, eg., Ca and Mg in fresh water (FV) and Na, Ca, Mg in seawater. . These metals readily exchange with aqueous phase protons or metal cations. A plot of the total amount of metal cations displaced by protons vs .. pH shows one inflection at pH 4 for FV algae and' in addition a second inflection at pH 2, 3 for marine algae. The first inflection is interpreted as. Indicating the cations associated with carboxyl groups ,and the ,second with half ester ?Sulfate groups. The exchange capacities of various aigal ,species vary widely. When FV algae is placed in a Pb2+ solution,- the amount of Pb2"' deposited on the algae is. Equivalent to the. Total Ca2?, Mg2, and H+ displaced? thereby confirming the ion exchange mechanism. Ion exchange equilibrium constants are reported for the displacement of ca2+ from Vaucheria. With Mg2+, sr2+, Cd2+, Pb2+_ and Na+ as well as the reverse reactions. Cd2+ can .be removed partially from algae by precipitating it as CdS or Cd(OH) 2 Pb2+ and Cu2+ are also partially removed as the hydroxides. Rates of reaction for various alkali hydroxides decrease with increasing .unhydrated cation radius. It is concluded that theory is useful in predicting viable applications for algae in pollution abatement.

Jan 1, 1991

By R. J. Davidson, N. Schoeman

SYNOPSIS The paper describes each of the stages in a carbon-in-pulp (CIP) or carbon-in-leach (CIL) plant, and details the steps that can be taken to achieve effective carbon management by referring to practices at the Daggafontein CIP plant. This approach was adopted because of the difficulty in summarizing current carbon management in the many varying operations in South Africa, Daggafontein being chosen as a high-tonnage dedicated well-run plant of recent design. Because of the major role played by the consumption of carbon in the operating costs of CIP and CIL plants, an attempt is made to develop a series of indexes based on quality parameters and price that can be used as a guide In the selection of carbon.

Jan 1, 1991

By Xinming Lu

In this paper, we use a new kind of fan charateristic curve instead of the common quadratic function, and give the existence and the uniqueness of the solutions to the ventilation network controlling equations, so that the existence and the uniqueness of the solutions for the natural air distributting problem can be conveniently given. We also give a conjugate gradient method with the global convergence to solve the equations having the unique solution. Because we adopt a very efficient technique of one dimensional search (or linear search) in this method, the method can quickly solve a lot of problems, especially in large scale problems. The second part of this paper is the establishment of the model of the constrained quadratic programming for the measurement adjustment of mine ventilation network. We give the algorithm to solve this model as well. The two algorithms given above have been realized in the mic-computer MC-68000 with Fortran codes, and the numerical results are satisfactory.

Jan 1, 1991

By Ashley P, Neale T

Alluvial gold was discovered on Sudest Island in 1888, and by 1893, an official production of 10 000 oz had been won by expatriate miners from shallow alluvial and colluvial workings. Hardrock sources were located and while one was developed at Mt Adelaide, production is unknown. Sudest Island comprises mostly phyllites and lesser coarse grained rocks which are cut by metamorphic quartz veins and basic (locally shoshonitic) intrusives. Sheared and altered basalts and serpent- inites represent are believed to be elements of an ophiolitic suite inferred to be associated with metamorphic core complex development and thus similar to tectonic environments on Misima and the D'Entrec- asteaux Islands. No epithermal-style quartz suggestive of a target similar to that on Misima Island has been identified on Sudest. A hardrock source for the alluvial and colluvial gold is interpreted to be metamorphic quartz veins similar to those in the Bendigo- Ballarat Zone of central Victoria, possibly remobilising gold derived from the meta- sedimentary and meta-igneous rock pile. The present focus is on development of a small scale alluvial gold mining operation in conjunction with exploration for hardrock targets. This latter programme remains at a reconnaissance stage.

Jan 1, 1991

By Kenneth L. Rubow, Virgil A. Marple, Ye Tao

Techniques are being developed for measuring the mass concentration of respirable diesel exhaust particles found in underground coal mines. Studies have been conducted over the past five years to investigate size selective sampling techniques to measure the respirable mass concentrations of diesel exhaust and mine dust aerosol particles in underground coal mines. Results from these studies have been used to develop design and performance criteria for a personal diesel exhaust aerosol sampler. Three personal diesel exhaust aerosol samplers have subsequently been designed and evaluated in both laboratory and field settings. These samplers use size selective classifiers for the determination of the respirable mass concentrations of mineral dust and diesel exhaust particles. Their designs are based on the premise that diesel exhaust particles are predominantly less than 0.8µm while mineral dust is greater than 0.8 µm. One design, selected for field evaluation, consists of a 10 mm nylon respirable dust cyclone followed by a 0.8 µm cutpoint impactor and afterfilter. The cyclone removes the large nonrespirable particles while the inertial impactor stage, collects the mineral dust on an impaction plate and allows the diesel particles to penetrate to an afterfilter. The two sample fractions of the respirable particles (<0.8 µm and >0.8 µm) are gravimetrically analyzed to determine the concentrations of the diesel and mineral dust portions in the respirable coal mine aerosol.

Jan 1, 1991

By J. W. Oberholzer

This paper describes research being undertaken by the Chamber of Mines Research Organization (COMRO) which is designed to assist the continuous miner operator and section foreman in the performance of their jobs. The project will initially provide visual assistance to the miner operator, and later will semi-automate the mining (cutting) process. Using a technique known as "RF tagging," the project will also provide real-time or near-real-time information about the performance of the loading and hauling units to the section foreman, allowing him to quickly detect problems and take action where appropriate. The project is based upon the application of currently available technology, and the first phase is scheduled for in-mine testing within the next year.

Jan 1, 1991

By Suresh K. Bhatt

This U.S. Bureau of Mines report reviews major developments in continuous haulage technology for underground coal mines. Haulage systems, both in use and under development, were investigated through a comprehensive literature search and visits to mines and manufacturers. The systems include flexible conveyor train, mobile conveyor, monorail bridge conveyor, multiple-unit continuous haulage, extensible, and belt turning systems. Strengths and weaknesses of the systems are assessed in light of their operating under remote control and their application to the computer-assisted continuous mining machine research being conducted by the Bureau. Through mining scenarios, candidate haulage systems are conceptualized to be consistent with the capabilities of the mining machine.

Jan 1, 1991

By Lu Peiyan

A computation model of soil-pile (wall) interaction under lateral loading is presented in this paper. The model has been applied to some engineering projects, and the comparison between computation result and measured result shows good agreement, so the model is proved to be correct and practical.

Jan 1, 1991

Inefficient conveyors suffer carryback, leading to the build-up of materials on idlers, and other expensive components. They spill and leak material at loading zones and transfer points, causing accumulations that can damage the belt, wear moving components, and increase both cleanup labor and maintenance expense. They wander or mistrack, spilling material and en- dangering personnel and conveyor components, including the belt itself. And through these inefficiencies, they multiply an operation&apos;s hidden costs-the dollars lost because of missed production, of increased downtime, of the expense for the replacement of prematurely worn or damaged equipment. In this paper, the author will examine the importance of belt conveyors to mines and process plants He will trace the state-of-the-art in systems for cleaning belts, and controlling the release of fugitive material from conveyor transfer points, by exploring the roots of the problems, and demonstrating solutions that have been proven to be effective. Included in these systems to improve material handling are transfer point stabilization and sealing systems, dual belt cleaning systems, and belt training idlers.

Jan 1, 1991

By J. C. Cawley

Improvements in today&apos;s maintenance practices are mandatory as more complex and productive machines evolve in the mining industry. By keeping machine reliability high, through improved maintenance procedures, overall mining costs can be reduced. The Bureau of Mines is investigating diagnostic maintenance systems for underground mining machinery. A hydraulic expert diagnostic system and an electric motor predictive diagnostic system have been designed and installed on a Joy 16CM continuous miner. An electrical diagnostic system has been designed and installed on a Joy 14CM continuous miner. Each system is functionally described and the relative merits of expert diagnostic systems versus algorithmic diagnostic systems are discussed.

Jan 1, 1991

By Sullivan T. D, Lohe E. M

Geological structure is one of the main controls on ground conditions within mining. It has a significant impact on the mining conditions and productivity of coal mines within the Sydney - Bowen Basin. The three main types of faults common to this region, normal, reverse and strike-slip systems, each present distinct challenges to mining. These systems effect a wide range of geotechnical and mining conditions within the mines. These include coal quality, strata stability, goat and caving behaviour, productivity and maintenance schedules of mining equipment, mine design and mine-site stress fields. A better understanding of the regional, local and mine-scale structural setting, timing relationships of structural events and the mechanisms of fault formation will greatly aid industry&apos;s push for greater productivity and competitiveness.

Jan 1, 1991

By K. F. Unrug

Martin County Coal Corporation is located in Martin County, Kentucky in the Appalachian coal fields, near the West Virginia border. The total leasehold covers more than 33 000 acres. Total annual production at Martin County Coal Corporation is currently 2,500,000 tons, but in certain years exceeded 3,000,000 tons. Approximately 45 percent of the annual production comes from two surface mines. The balance is produced from five underground mines. Martin County Coal Corporation&apos;s work schedule consists of 240 days/year, two nine-hours shifts/day.

Jan 1, 1991

By Young DJ

Gold mineralisation at the Hamata prospect is related to a series of stacked pyrite and quartz-pyrite veins associated with a number of shears which strike N to NE and dip E. Mineralisation is contained entirely within the Morobe Granodiorite close to the intersection of the Upper Watut Fault and some younger NE to SW striking faults. The prospect was originally detected in 1987 by a regional stream sediment sampling programme. Subsequent mapping and sampling outlined an anomalous zone approximately 900m long by 300m wide. Drill testing has indicated a resource of 46Mt at 0.9 g/t Au.

Jan 1, 1991