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By Steven D. Wirch

Abandoned underground coal mine areas must either be sealed or ventilated to comply with federal mine regulations. Ventilation of these abandoned areas is often impractical due to roof falls and inadequate primary mine ventilation. If the area is sealed, a very complex ventilation system is set up. In which the gob "breathes" in and out due to barometric pressure fluctuations. The Gob Assistant is a computer program (for use on IBM compatible personal computers) which allows the prediction of air flows into and out of a sealed mine area. Gas flows with applicable control techniques are also modeled. This information is presented to the user who will decide which control technique, or combination of techniques will ultimately be applied. The Gob Assistant is an intelligent gob simulator that can reduce the guesswork involved in predicting the effects of sealing and control techniques before they are applied. This paper provides the fundamental principles upon which the Gob Assistant is based, verification of these principles, and an explanation of how these principles were integrated into the Gob Assistant.

Jan 1, 1988

By R. V. Ramani, R. Bhaskar

"The National Academy of Sciences (1) recognized the importance of studying the spatial and temporal characteristics of respirable coal mine dust atmospheres. In this paper, the progress to date of a research project on dust transportation and deposition in mine airways is presented. A mathematical model is proposed for studying the transport of dust. A source representative of dust generation in underground coal mining is defined. The influence and applicability of surface roughness, dispersivities, coagulation and reentrainment to vine dust flow arc examined. A convective-diffusion model is proposed for the transport and deposition of dust in mine airways. Using the model, the spatial and temporal characteristics can be evaluated in terms of dust concentrations in the mine atmospheres.INTRODUCTIONThe prediction of the behavior of fine particles Is Important in many fields of science and engi¬neering including physics, chemistry, mining, mineral processing, and atmospheric science. In mining from the health point of view, fine coal dust is associated with the appearance of pneumoconiosis in miners exposed to the dust. Also, in addition to being a nuisance factor obscuring visibility and general mobility of miners, it can lead to sudden catastrophic incidences of explosions. This paper outlines the progress to date of a research project on dust transportation and deposition in mine airways. A mathematical model is proposed for studying the transport of dust for the various mechanisms. The dust dispersion is defined in terms of a dispersion term determined from experimental data by Skubunov (23). Coagulation is considered as one of the mechanisms that can lead to changes in the particle size distribution. Reentrainment as a possible secondary source of dust was examined during model development but was not included in the final model."

Jan 1, 1988

By Roberts M. L

Long Shaft was initially developed using a rail haulage system on every working level comprising battery electric locomotives and granby trucks loaded by rail mounted rocker shovels. Production was commenced using conventional hand held cut and fill mining methods. In an effort to improve productivity and reduce operating costs a mechanised cut and fill stoping method evolved to suit the wider sections of the orebody. To further improve productivity and reduce costs the mechanised levels of the mine are progressively being redeveloped to enable the use of trackless diesel haulage equipment. An added benefit of trackless haulage equipment will be the ability to place development mullock into stopes as Fill.

Jan 1, 1988

By E. S. Erickson, R. L. Stone

Introduction Evidence from blast furnace operations has indicated that using pellets with a higher ISO low temperature reducibility, a lower SiO2 content, and better resistance to low temperature degradation results in considerable coke savings and improved furnace operation. Although these benefits could not be directly related to reducibility differences alone, we believed there was sufficient evidence of the advantages in improved pellet reducibility to warrant laboratory investigation of ways and means to effect such improvements. It is well known that pellet reducibility can be significantly altered by changes in the basicity and the amount of non-iron oxide constituents. Past work (Friel and Erickson, 1980, 1982; Saeki et al., 1977; Thanning, 1974) has shown that with increased MgO contents, and at optimum CaO/S1O2 ratios, significant improvement in low temperature reducibility can be attained. The improved properties of such fluxed pellets have reportedly led to increased blast furnace efficiency and productivity (Saeki et al., 1977; Ilmoni, 1975). Less well known, however, is exactly what factors control reducibility in acid pellets. Because of this gap in knowledge, studies were undertaken of the factors affecting reducibility in acid pellets and to estimate their relative significances in modifying reduction behavior. This paper describes that part of our work done to determine the effect of bentonite on reduction behavior. Our approach was to first examine the effect of bentonite's presence on as pure an iron oxide as possible (i.e., a magnetite "superconcentrate" containing about 0.2% SiO2) so as to eliminate any gangue-binder interaction. The next step was to look at bentonite effects on concentrates with only limited amounts of gangue (containing about 1% SiO2), but of two different types, simple and complex silicates. Last, we

Jan 1, 1988

By Koginmo V. I

The concentrator at Bougainville Copper Limited has an annual throughput of 48.2 million tonnes/year producing approximately 175,000 tonnes copper, 16.1 tonnes gold, and 50 tonnes silver. Conventional three stage crushing and screening are used to reduce run of mine ore to an average product d80 size of 6.7mm. The primary objective of the crush- ing plant is to provide a continuous supply of ore to the 12 primary grind- ing mills via an intermediate 300,000 tonnes capacity stockpile. Since ball mill performance improves with decreasing mill feed size, the crushing plant continually strives to produce the finest possible product for mill- ing. This has been achieved by increasing plant availability and total installed power, and improving crusher manganese liner life, screen cloth life, and plant operating practices. A recent innovation was the installa- tion of a 35 million tonnes/year preconcentration screening plant in Janu- ary 1987 to recover high grade fines from low grade run of mine ore types in which the mineralisation occurs preferentially along fracture planes in the parent rock.

Jan 1, 1988

By Wernick B. J

Recently, the Environmental Engineering Laboratory of the Chamber of Mines of South Africa Research Organization has made signifi- cant progress in the development of more accurate algorithms for assessing heat flow in gold mines. These algorithms have been incor- porated into an overall computer program, ENVIRON, which enables the complete thermo- dynamic analyses of mine ventilation and cool- ing systems to be carried out. Recently, efforts have concentrated on the development of an expert computer system which will guide engineers in the process of selecting the most appropriate environmental control strategy.

Jan 1, 1988

By D. W. Horsfall

The different types of processes used in fine coal beneficiation in the Republic of South Africa are listed, together with data giving an indication of their separating efficiencies The two classes of coal, fines and ultra-fines, present in the -0,s m fraction of the run of mine coal are discussed, with special reference to their beneficiation characteristics. Using those properties, together with the data on plant efficiency, case studies are worked out to indicate the advantages and disadvantages of the different processing routes available. The paper closes with an indication of areas where research is required to enable some of the processes to be applied to a greater extent than is presently the case.

Jan 1, 1988

By E. O. Stensholt

The Hybinette electrorefining process for production of cathode nickel was in use at Falconbridge Nikkelverk A/S, Norway, until 1975 when conversion to the new chlorine leach process was started. In 1978 the conversion to electrowinning had been completed, but further major improvements to the process have been made up to 1987. After a major expansion program in 1985 - 87 the refinery has a nickel capacity of 54 000 mt Ni/year. The main feed materials to the process are converter matte from the Falconbridge smelter in Sudbury, Ontario, Canada, and from the BCL smelter in Selebi-Phikwe, Botswana. A typical composition of the mixed feed to the refinery is: 40 - 45% Ni, 25 - 30% Cu, 20 - 22% S, 2 - 3% Fe and 1.0 - 1.5% Co. The matte is chlorine-leached in the first process step, nickel being dissolved selectively in a train of leach-cementation tanks. Essentially all copper and sulphur that was present in matte appears in the leach residue as CuS. In 1986 an autoclave treatment stage was added to the process to improve nickel extraction from the leach residue. The resulting strong nickel chloride solution is purified by the process steps (1) precipitation of iron and arsenic, (2) solvent extraction of cobalt and other minor elements and (3) precipitation of lead and the remaining impurities. The nickel solution is then fed to the tankhouse, where various nickel products are produced by electrowinning. The chlorine gas that is produced during the electrolysis is returned directly to the chlorine leaching tanks to dissolve more matte. After stripping from the loaded organic phase and solution purification cobalt is also produced by electrowinning. The copper sulphide leach residue, which contains some nickel, is dead- roasted in fluidized-bed roasters. The sulphur is recovered and sold as sulphuric acid. The calcine is leached in spent copper electrolyte, from which cathode copper is produced by electrowinning. Precious metals and the remaining base metals are recovered from the copper leach residue. The Falconbridge chlorine process is very versatile. It can accept a wide range of impurities in the feed and still produce metals of exceptional purity.

Jan 1, 1988

By S. Vijayan

Despite the limited demand for rare-earth elements, as well as yttrium and scandium, in conventional applications, the emergence of ne~ high-technology applications such as supermagnets, lasers and superconductors is expected to result in significant demand for some of these elements. This paper examines the anticipated applications and demands for rare-earth elements over the next decade and their implications on the utilization of available resources. Process methods for the recovery of rare-earth elements from conventional and unconventional resources are reviewed in the context of their growing demand. Challenges facing the industries in meeting this opportunity are also discussed.

Jan 1, 1988

By N. Greninger

The Bureau of Mines conducted a laboratory study of the measurement of the water and rock dust (RD) contents of synthetic mine-type coal dust (CD) mixtures using a commercial unit for measuring water content and several prototype radiometric units for measuring the RD content. The RD content ranged from 50 to 100 wt pct and the added water (AW) ranged from 0 to 15 wt pct. The total water (TW) content (intrinsic (IW) and AW) of a small dust sample could be readily measured automatically by essentially untrained personnel using a commercial unit. The RD content of a sample containing only IW could readily be measured by moderately trained personnel using several radiometric units. With gamma-ray devices, about 300 g of sample is needed. With the improved beta-ray device, about 25 g of sample is needed. With dry mine dust samples, the estimated RD error range for gamma-ray devices is 0.8 to 2.3 pct and 0.5 to 1.0 pct for beta-ray devices. However, the radiometric measurement of RD content was questionable if the dust mixture also contained AW or if it was uncertain whether the dust mixture contained AW.

Jan 1, 1988

By A. Sheikh, S. Hardcastle

"Various methods of leaching are being used by Denison Mines Ltd. Uranium Operations. This study was designed to investigate the flood leaching operation of two parallel inter-connected stopes contained by pressure bulkheads. The teaching muck piles, created from large scale uppers production blasts, are aerated by compressed air lines laid beneath the pile prior to blasting.A SFr, tracer gas, injection technique has been employed to determine the post-blast integrity of the single-ended air distribution system. SF6 was injected into the compressed air line feed to the stopes and collected at borehole exhausts from the stopes in grab-sampling bags. Analyses of the air samples were performed with a gas chromatograph.The system was designed to give a sufficiency of oxygen to sustain bacterial activities used to enhance the leaching recovery in the muck piles. The results obtained indicated that there is a minor anomaly in the distribution system that may not be critical to the operation. Compared to an idealized case, the over-all efficiency of aeration throughout the muck is estimated at over 85%."

Jan 1, 1988

A computerised influence function approach to subsidence and horizontal displacement prediction is described, with particular emphasis being placed on the applicability of the method to irregular- shaped mine workings. Based on previous work [1], this approach has been put for- ward for inclined seam situations. Examples of graphical output presenting surface subsidence contours, horizontal displacement vectors and principal strain vectors are given and their significance discussed in relation to current problems.

Jan 1, 1988

By David S. Bolin, Gary R. Peterson

INTRODUCTION In both the United States and Canada, a company making a public offering of securities must comply with regulations which have been promulgated by Federal and/or Provincial Legislatures. This paper focuses on the regulations pertaining to reserve reports required by the United States Securities and Exchange Commission (SEC). SEC RESERVE FILINGS Reserve reports made to the United States Securities and Exchange Commission are the only reserve reports which are directly regulated by the United States government. The requirements for SEC reserve reports are set forth in the filing forms as shown in Appendix A, from Item 17A of SEC Form S-18. These reporting requirements, which are intended to protect the investing public from inaccurate or misleading claims, are primarily oriented to S-1 or other filings for new stock issues but must also be followed for annual 10K reports which must be filed annually by U.S. public corporations as part of the Corporate Annual Report. These undertakings require independent audits of reserves, mine designs, plant facilities and a general economic evaluation of the planned or existing operation as part of the backup documents for filing. An ore reserve is defined by the SEC as "That part of a mineral deposit which could be economically and legally extracted or produced at the time of the reserve determination". This definition is unchanged since it was last

Jan 1, 1988

By S R. "Bob" Pilshaw

Productivity is the popular "buzz" word that catches the attention of most managers when it is featured in the more popular mining and construction magazines. Engineering Task Forces and teams are formed to take advantage of productivity opportunities in almost all phases of an operation except the drilling and blasting area.

Jan 1, 1988

By Akira Yazawa

To realize highly efficient process in extractive metallurgy, continuous operation nearly in equilibrium is preferable, but most metallurgical processes consist of plural steps with different chemical potentials. Traditional two-step process of sintering followed by reduction is continuous in each step, but is heterogeneous reaction system far from equilibrium, and the chemical potentials are varied considerably along the distance the charge travels in a reactor. This route will become old-fasioned in next century due to the various inherent problems caused especially by sintering process. To establish reasonable new smelting processes, the important tasks of the metallurgists are how to introduce feed and reacting gas in the reactor, and also how to overcome the difference in chemical potential in the reactor system. Based on the ways to solve theses tasks, recent proposals of new smelting process for copper and lead are classified and discussed with the help of sulfur-oxygen potential diagram. On such potential diagram, each equilibrium step in continuous smelting is expressed at a fixed point, and two reactors with different chemical potentials must be connected by continuous molten flow through launder or partition wall. In the latter case, the reactor is apparently single, but some technical problems must be overcome. While, in a batch smelting like converter, potential variation is successively realized along a path on chemical potential diagram with the time elapsed. To establish immediate equilibrium, continuous steady flow of reactants into well mixed reactor is indispensable. In modern smelting process, the ore is mostly supplied in the form of powder which have huge surface area and fluid character, and consequently injection process must be very attractive. Several examples are discussed for both of copper and lead smelting, and promising future technologies are suggested.

Jan 1, 1988

By J. A. Cruise

From 27th to 29th September, The South African Institute of Mining and Metallurgy held a Colloquium on Equipment Alternatives in Underground Mining in Johannesburg. The Colloquium, which was highly successful, was held concurrently with the 1988 Electra Mining Exhibition. Particle characterization The Fourth European Symposium on Particle Characterization is to be held in Nirnberg, West Germany, from 19th to 21st April, 1989.

Jan 1, 1988

The hazard posed by underground mine fires is illustrated in the first part of this paper by means of a review of experiences in four mining countries over the last three decades. This brief review indicates that while much progress has been made generally in preventing fires and providing means of protection to miners, the possibility of disasters occurring must continue to be regarded as very real. Based upon recent investigations by the South African mining industry, an integrated strategy for providing protection to personnel in the event of a fire is outlined in the second part of the paper. The main, complementary, elements in this strategy are the prevention of ignitions, the limitation of fires, provision of protection systems and equipment, training for emergencies, and effective implementation of safety measures. Some comments are made on important aspects of these elements and on possible further developments.

Jan 1, 1988

By S. Suzuki, Y. Maeda, N. Wakamatsu

"A new pyrometallugical technology, named KLS process, has been developed by Dowa Mining at its Kosaka Smelter to smelt various kinds of lead raw materials.The process consists of clearly separated two reaction steps, smelting and reduction. For this purpose, respective stationary furnaces are installed which are connected by a slag launder.Dry raw materials, together with pulverized coal and oxygen-enriched air, are injected through a lance pipe into the molten slag in the first furnace. It is kept under a high oxygen potential to remove sulfur completely. Resultant PbO rich slag overflows to the second furnace where pulverized coal and insufficient air are also injected through a lance pipe to reduce PbO to lead bullion and to compensate for thermal deficit. The entire operation is carried out continuously. The process development started back in 1981. In late 1986, a pilot plant with a capacity of 3.5t/H was constructed.Already nearly 20,000 tons of raw materials, mostly lead sulfate mixtures have been smelted successfully.IntroductionFor a long time, main raw materials for lead smelting at Kosaka smelter have been such secondary incombustibles as lead sulfate and lead-barium sulfate. The former is leach residue of the copper smelter flue dust and the latter originates from Iijima zinc refinery. While the most of lead concentrates produced locally has been smelted by an ISF of Hachinohe smelter in which Dowa Mining has a share.The surplus lead concentrates were processed at Kosaka by a hydrometallurgical method to convert PbS to PbSO 4 as pretreatment, and followed by simultaneous smelting together with the above secondary materials (1). Approximate output has been 1,5000 /M of lead bullion and slightly more than 2,000t/M of refined lead by adding lead bullion returned back from Hachinohe smelter (2)."

Jan 1, 1988

By James C. Cawley

This report presents results of recent Bureau of Mines research to establish the probability of spark ignition as a function of current (or voltage, for capacitor circuits) for resistive, inductive, and ca-pacitive circuits in 8.3% methane-air atmospheres. The data presented quantify the explosion hazard created when low-power electronic devices catastrophically fail in an explosive mine atmosphere. Previous litera-ture dealt with levels of probability between 10-3 and 10-4. This re-port extends the probability data to levels as low as 10-7. This study has verified that when the probability of ignition, PI, is plotted on a log-log coordinate system versus the current (or voltage), a continuous, straight-line relationship is formed. An interesting result that can be statistically hypothesized is that at some low level of igniting current the ignition process ceases altogether.

Jan 1, 1988

By N. S. Dalal, V. Castranova, X. Shi, W. Wrr, V. Vallyathan

"SUMMARY Data presented here indicate that freshly fractured silica exhibits surface characteristics and biologic reactivity distinct from aged silica, and on this basis we propose that these surface features may lead to enhanced manifestations of lung Injury. Grinding of silica produces ~10"" Si and SI-O (silicon-based) radicals per gram of dust on the particulate surface which are characterized by an electron spin resonance (ESR) spectrum centered around g = 2.0015. These silicon-based radicals react with aqueous media to produce OH radicals, which are demonstrable using a DMPO spin trap. The concentration of silicon-based radicals in silica decreases with aging in air and exhibits a half-life of ~30 h, whereas its ability to generate OH radicals in aqueous solution decreases with a half-life of ~20 h. However, on storage in aqueous media, the concentration of silicon-based radicals end the dust's ability to generate OH radicals decrease significantly within a few minutes. Freshly ground silica is also more biologically reactive than aged silica, because freshly crushed silica activates a greater respiratory burst In alveolar macrophages than aged silica, i.e., storage of ground dust in air decreases silica-Induced superoxide anion secretion, hydrogen peroxide release, and NBT reduction by 25%, 68%, and 43%, respectively. Furthermore, compared to aged silica, freshly ground silica exhibits a greater cytotoxic effect on cellular membrane Integrity, i.e., a 1.5-fold increase in LDH release from macrophages, a 36-fold increase in hemolytic activity, and a three-fold increase in the ability to induce lipid peroxidation. Because acute silicosis is frequently associated with occupations in which freshly fractured crystalline silica of respirable size is generated, the present study suggests that fracture-generated silicon-based radicals may play a significant role in the pathogenesis of this disease. AM REV RESPIR DIS 1955; 133:1213-1218IntroductionOccupational exposure to crystalline silica can be associated with either chronic or acute pulmonary disease. Chronic silicosis becomes manifest 20 to 40 years after first exposure and is characterized by development of concentric hyalinized nodular lesions in the lung with the de-velopment of dyspnea over a period of several decades. Acute silicosis, on the other hand, is manifested by a rapid on-set after exposure and is characterized by the accumulation of an amorphous granular lipoprotein exudate in the airspaces and rapid development of respiratory disability within a few years (1-3).Information is growing concerning the etiology of chronic silicosis. Studies sug-gest that several mechanisms may be in-volved in the development of fibrosis. Lung injury may result from silica-induced release of lysosomal enzymes from alveolar macrophages (4, 5). In ad-dition, silica-induced activation of su-peroxide anion and hydrogen peroxide release from alveolar macrophages may result in oxidant-induced damage to lung parenchyma (6). Silica exposure can also result in the release of mediators from alveolar macrophages which enhance the proliferation of fibroblasts and the syn-thesis of collagen by these pneumocytes (7, 8)."

Jan 1, 1988