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By G. B. Misra

Attempts have been made during the last three decades to establish a correlation between respirable dust dosage and the degree of progression of pneumoconiosis or silicosis amongst mine workers. Fair correlation has been possible only after the Johannesburg Pneumoconiosis Conference established mass concentration of dust in the respirable size range as the true measure of the incidence of pneumoconiosis. The author had established a good correlation between cumulative total respirable dust dosage as well as cumulative silica dosage and the category of pneumoconiosis according to ILO classification at Mufulira Copper Mine. Studies at Hutti also show a linear relationship between the average cumulative dust and silica dosage md the category of pneumoconiosis. However the maximum tolerable cumulative dust dosage for - prolonged exposure is 182 mg month/m3 - at Hutti as compared to 275 mg month/m3 at Mufulira. Similarly the maximum tolerable silica dosage for - prolonged exposure is Only 35 mg month/m3 at Hutti as compared to 55 mg month/m3 at Mufulira. The TLV for dust concentration at Hutti works out at 0.6 mg/m3 compared to 1.1 mg/m3 at Mufulira and the TLV of silica concentration at Hutti is 0.117 mg/m3 compared to 0.25 mg/m3 at Mufulira. The Hutti figure is however, closer to the TLV of 0.1 mg/m 3 recommended by ACGIH.

Jan 1, 1987

By C. F. Meyer

The recirculation of mine air in an underground colliery, has always been regarded as a hazardous practice in South African collieries. The Mines and Works Act and Regulations states that fresh air, flowing Into an underground section, must flow out directly into the return airways after being utilized once in the section. One of the largest producing underground collieries in South Africa, Initiated a project on controlled recirculation with the permission of the South African Government Mining Engineer. The project involves the recirculation of 65 m3/s of air inside a ventilation district which serves a total of six production areas. The aim of the project was to increase the airflow to the sections without altering the existing ventilation system. Tracer gas studies were carried out to determine the actual distribution of the recirculated air to the individual areas. The results showed that an effective 54,18 m3/s of the recirculated 65 m3/s reaches the sections. This gives an air utilization figure of 83,4 per cent. Dust surveys were also carried out as part of the project to determine the effect of the recirculation of the return air on airborne dust levels. The results showed that the dust levels remained constant in the main intake and return airways and that no hazardous situation was being created. The project proved to be successful and showed that controlled recirculation can be executed and used as a solution for the supply of air to sections without endangering any lives.

Jan 1, 1993

By R. Latifovic

Assessment of the possible impact of existing and future mining projects located in remote areas may be difficult and costly. This may have an adverse effect on the process of issuing mine permits and development of new mines. A remote sensing based land cover change assessment methodology presented in this paper is a promising avenue to render this process more meaningful, precise and affordable. It has been applied to a case study of the Oil Sands Mining Development in the north-east of the Canadian province of Alberta. Recently, the Athabasca Oil Sands Region (AOSR) is a place of unprecedented growth of open-pit mining operations. This study was focused on the primary impact onto the landscape and vegetation resulting from exploration and, mining development. This impact was assessed using an information extraction method applied to two LANDSAT scenes. The analysis based on derived land cover maps shows a 8.64% decrease of natural vegetation in the study area (715,094 ha) in 2001 relative to 1992. It is demonstrated that the methodology presented here provides reliable results and is fully applicable for the assessment of the environmental impact of large scale mining operations.

Jan 1, 2006

By Maurice C. Fuerstenau, Bruce R. Palmer, R. E. Johnson, B. R. Palmer, G. W. Warren

The environmentally sound processing of metal-bearing chloride solutions plays a key role in the extraction, plating, recycling, finishing and surface preparation of metals. Additionally, many chloride-bearing waste streams must be processed to obtain environmentally acceptable products. This paper reviews the technologies used for processing aqueous metal-chloride solutions and describes the challenges that have been overcome in application of these technologies.

Jan 1, 1993

By Douglas W. Fuerstenau

This paper concern the specific adsorption of sulfate anions on nonmetallic minerals and its role in flotation. The specific surface affinity of sulfate ions in various systems has been observed in the results of electrokinetic measurements that show conditions under which sodium sulfate can reverse the sign of the zeta potential. The electrical double layer model provides a means for interpreting the results and for estimating the free energy of adsorption of sulfate ions. Because of their surface activity, sulfate ions not only can function as a depressant in the flotation of oxide minerals with physisorbed anionic collectors but also can function as an activator for flotation with physisorbed cationic collectors. Their role in depressing or enhancing the flotation of the sparingly-soluble mineral barite is also explained in terms of the double layer model.

Jan 1, 2005

This paper discusses how the link between design software tools and recycling models can be established in order to predict the recyclability of the car during the design phase, as well as to be able to apply design for recycling on a solid technological basis. Due to the complexity of the design of the car, optimisation of recycling can only be realised based on a sound technological basis, in which the dynamic and statistically distributed parameters affecting the recycling rate are described and understood. This paper gives a brief overview of the dynamic and recycling models, which are developed for optimisation of the recycling of the car and the calculation of recycling rates of the car in the design phase in view of EU legislation. Moreover the possibilities for modelling of shredding and liberation within the recycling system are discussed. The performance of experiments on a fundamental basis in order to collect statistically correct industrial data, supported by a closing mass balance, is referred to on the basis of a large scale industrial recycling experiment. It will be shown how design for recycling and environment can be supported by the sophisticated models as developed by the authors.

Jan 1, 2005

By T. Yalcin

It is well recognized that machine type and machine characteristics play vital roles in the successful application of froth flotation in mineral processing. Since the early 1900s, a multitude of machine designs have been and are still being introduced in an attempt to improve flotation efficiency. Machines based on mechanical agitation have been the most dominant in industrial practice. However, in recent years there has been a growing interest in pneumatic flotation units because of their claimed simplicity, low cost, high throughput and good metallurgical performance. This work was carried out to assess the effectiveness of pneumatic flotation on a magnetite ore. The method was applied using a prototype pneumatic flotation device that utilized a suitable nozzle for bubble generation. Important variables of the process were examined and optimized, including the nozzle size, air flow rate and froth thickness. Further tests were conducted to determine the influence of frother dosage and to explore the improvements that could be made on concentrate grade and recovery by cleaning and scavenging. Under the best test conditions, an iron concentrate was obtained with a grade of 66.4% Fe and a recovery of 97.7%. Particularly, the recovery was superior in comparison to that of mechanical flotation. This was attributed to the ability of pneumatic flotation to create and maintain a relatively thick froth layer.

Jan 1, 2002

By Qing Wang

Open pit mines require substantial capital investment at the beginning of the operation and replacement investment at later years. The objective of obtaining the highest possible return on investment in a mining project can only be achieved with an efficient long term production plan. This plan consists of optimally determining four principal elements: 1) the amount of ore and waste to be mined each year, 2) the specific blocks to be mined each year, 3) the optimum mine life, and 4) the ultimate pit limits, which delineate the total reserve to be mined. The existing methodologies only provide solutions to one or two elements, by assuming the others known. Furthermore, the cost of mining each block in the deposit is assumed to be known and independent of the production schedule. The four elements of production planning are interrelated and the cost of mining any block is a function of the production schedule. The ultimate goal of this study, ,whose first steps are' discussed in this paper, is to develop a solution methodology that can simultaneously optimize all four elements of the production planning problem in open pit mines without making a priori assumption on any of the four elements.

Jan 1, 1992

By J. F. Stenebråten, W. P. Johnson, D. R. Brosnahan

Carbonaceous materials (CM) from ores of varying preg¬robbing activity from Barrick Goldstrike Mines Inc. (BGMI), Nevada, were characterized in terms of their functional group contents, hydrocarbon contents, elemental composi¬tions and humic acid contents. Fourier transform infrared (FT-IR) analyses did not show the presence of hydrocarbons or carboxylic, phenolic or sulfhydrolfunctionalities. The FT¬IR bands present included C=C stretching in aromatic rings and C-O-C stretching, indicating the presence of oxygen as ether linkages or thiocarbonyl functionality in the carbon matrix. Calculated atomic oxygen to carbon (O/C) ratios did not reveal a trend between the maturity of the CM and the preg-robbing behavior, possibly due to the low resolution inherent in electron microprobe analyses. However, the atomic O/C ratios agree with other chemical analyses, indi¬cating that the organic carbon is very mature, similar to or higher than anthracite grade coal. Gas chromatography¬mass spectrometry and nuclear magnetic resonance analy¬ses corroborated the relatively featureless character of the carbon, indicating that the carbon structure is virtually completely aromatic (graphitic).

Jan 1, 2000

By M. McPherson, P. Mousset-Jones, G. Danko

Calculation of the sensible heat transfer between the rock surface and the flowing air in an underground airway is still fraught with problems. There are only a few results available in the literature for the calculation of the convection in tunnels with naturally rough surfaces. Some of them are purely empirical, while others use a theoretical approach, based on the analogy between heat and momentum transfer, expressing the heat transfer coefficient as a function of the friction factor. A review and evaluation of these results are presented. The heat transfer equations obtained using the different assumptions, vary over a wide range, so that experimental results are needed to determine the formulae and constants applicable to mine airways. In situ measurements of the "physical" and "technical" heat transfer coefficient carried out in deep mines are described. The statistical distribution of the convective heat transfer coefficient on rough surfaces, as well as the regression between the Nusselt and Reynolds numbers in the turbulent flow region, are presented. Radiative heat transfer between the surface and the moist air flowing in a duct of relatively large hydraulic diameter has been taken into account during evaluation. The results will be a definite refinement of those calculations presently used in mine climate simulation models.

Jan 1, 1987

By Jeffrey M. Listak, Gregory J. Chekan

The U.S. Bureau of Mines, in an effort to improve coal conservation and utilization is currently investigating longwall panel layouts to maximize coal recovery and minimize interactive problems in multiple-seam operations. When longwalling coalbeds in descending order, the transfer of stress from overlying gate roads is a major design constraint affecting pillar stability in the lower mine. The lower mine gate road pillars must be properly designed to withstand the additional load transfer if gate roads are superpositioned in successive seams. The Bureau's MULSIM/NL model was used to analyze load transfer mechanics for superpositioned gate road pillars. Analysis of Longwall Pillar Stability (ALPS), which is an empirically based design method for longwall gate road pillars, was used to calibrate model input parameters. The attributes of both the MULSIM/NL model and ALPS were combined to develop a modified method for estimating pillar stress for multiple-seam cases. The modified method uses a multiple-seam (MS) factor to estimate the stress on the lower mine gate road pillars when superpositioning is practiced. Numerical analysis shows that the MS factor is dependent upon the interburden thickness and pillar width and is presented in a series of graphs relating these two parameters. Several examples are included to illustrate the use of the MS factor for estimating lower mine pillar stress and resulting stability factors.

Jan 1, 1992

By R. W. Smith

Though generally rather non-selective in nature long chain collectors nevertheless function in different ways in accordance with their own particular physical characteristics. Altering various parts of their structures such as chain length, type of chain, etc. can therefore substantially alter the adsorptive behavior of the collectors in a set environment. The effect of such structural differences of the collectors on physical parameters such as solubility, critical micelle concentration, acid or base strength, tendency to be expelled from the aqueous phase is discussed, as is also the effect of these parameters on flotation behavior.

Jan 1, 1989

By Richard D. Harvey

Relative quantitative analyses of certain mineralogical and textural properties of carbonate rocks were made with an image analysis computer. The instrument, referred to by its manufacturer as a Quantimet; consists of a petrographic microscope, a television camera and monitor, a detector, an electronic computer, and a read-out meter. Measurements were made on polished and etched specimens, standard thin sections, and on scanning electron micrographs of carbonate rocks. Critical to the success of the analysis is the preparation of the specimen in such a way that good optical contrast is obtained between the various petrographic components. The dolomite content, the pore volume, pore boundary projection, and pore size distribution of high-purity carbonate rocks were measured by image analysis methods. The frequency and size distribution of void inclusions in dolomites were determined by image analysis of scanning electron micrographs of cleaved surfaces. Image analysis methods permit rapid and quantitative assessment of various microscopic properties. The results are of reasonable accuracy and certainly are relative quantities that may be used to characterize carbonate rock materials.

Jan 1, 1972

By M. McPherson, G. Danko

Methods of measuring in situ rock thermo-physical properties are rapidly evolving. Among those existing in the literature, a particular measurement procedure was selected for further development. The measurement is based on creating a spherical temperature field in a drill hole using a point source heater of constant heat flux. The bivariate temperature distribution 0 (r, t) is measured at several points along the length of the drillhole, radius r from the heater and at particular time intervals (t). A number of different evaluation methods were tested for calculating the unknown thermal conductivity (k) and diffusivity [] from the measured temperature and the known heat flux. The results showed that evaluation using the finite difference scheme and small temperature differences measured at points close together, cannot give a reasonable result. In order to solve the problem a new general analytical evaluation method is developed. Using an appropriate technique, it is possible to simultaneously obtain values for k and [], incorporating a semi least square technique to reduce the uncertainty in the evaluation. The new device and evaluation method makes it possible to obtain from a single drill hole highly precise k and [] values within an 8 hour period. The method has been used in several underground mines in the U.S. with good results.

Jan 1, 1987

By Mark S. Dunsbier, Steven J. Schatzel

Large roof outbursts began occurring in November 1986 at Domtar's Sifto Salt Mine in Goderich, Ontario, Canada, working the bedded Salina A-2 Salt unit. The outbursts, measuring about 13-20 m in diameter, released high concentrations of methane from cavities that extended into carbonate roof units. Spontaneous ignitions of methane gas during an outburst seriously burned a mine technician. The Canadian Ministry of Labour contacted the U.S. Bureau of Mines for technical assistance to aid in mine managements1 efforts in alleviating the problem. Initial gas content determinations of salt samples from the outbursts by acoustic test methodology revealed no methane enrichment. In- mine core drilling and subsequent methane content testing indicates the main source of methane in overlying roof units. Drilling the roof units demonstrated the potential of draining methane from areas showing signs of impending outbursting and alleviating the danger. Three mechanisms are considered the most likely means by which methane was introduced to the mine environment. These are (1) hydrocarbon gases released from brines, (2) gas transport along horizontal bedding planes or gas accumulations in bedding separations, and (3) mining-induced fracturing. The abundance of higher hydrocarbons in gas yielded by non-evaporite rock samples from the Goderich mine may be indicative of a former association with liquid petroleum.

Jan 1, 1989

By Joe Komadina

DOUG HALBE: Our next topic is one that I would think everyone might want to contribute to. I'm sure everyone here has had some experience in this area. If you haven't, I'd suspect you've never really run a mill. This is what we call "Horrible Spill Areas We Had When We Started Up the Plant and How We Fixed Them." Our next speaker has had a really great operating career. He had many years with Newmont in the Carlin area, and now he's executive vice president and chief operating officer of Independence Mining Company: Jim Komadina. I don't have to be nice to the speakers anymore, do I? [laughter] You may wonder why we picked Jim Komadina to give this talk. I was involved many years ago in the start-up of Newmont7s Gold Quarry plant. Jim held quite a responsible position there. I'm not going to say anymore, but I have in the back of my mind this picture of the pump floor and a rowboat and a guy rowing around on the pump floor. [laughter] Jim, was that you? [laughter] JIM KOMADINA: Probably. I wasn't responsible for the design. [laughter] Actually it's amazing. I've seen a lot of these plants and actually had the opportunity to walk around them, so when I say this, "Horrible spills I have seen and done," it's because I've been responsible for more than my fair share of them. But having seen a lot of spills, I will present a little bit of wisdom about how to prevent them.

Jan 1, 1998

By Randal J. Barnes

The nonlinear network optimization algorithm developed in this paper solves the following mine ventilation design problem: find the location and size of all fans and regulators which minimize the overall system power consumption while satisfying all physical, legal, and operational constraints. This work includes the formulation of the problem within the framework of mathematical optimization, the development of the computational theory, and the creation of an efficient solution methodology. The algorithm has been implemented on a microcomputer, and a small but representative example is included. The algorithm presented in this paper has four limitations. First, the optimization process is for a single point in time: the dynamic nature of a mine ventilation system in an evolving mine is not directly addressed. Second, the topology of the ventilation network is required input information. The mathematical algorithm does not optimize the size or location of the mine ventilation airways; however, the post optimality analysis techniques can be used to aid in topological decisions. Third, the problem is formulated using volumetric flow; thus, heat and moisture transfer are ignored. Fourth, the capital cost of ventilation equipment is not included in the formulation.

Jan 1, 1989

In the UK as existing face capacity is replaced, many of the new faces will have higher installed powers and be located in zones of higher strata temperature. These factors coupled with the need to increase production will result in more faces experiencing environmental difficulies, especially with respect to climatic conditions. In many cases these problems are unlikely to be solved, as in the past, by simply increasing the face air quantity. Therefore other techniques including refrigeration will be necessary, possibly requiring major capital and operational expenditure. It is easy to spend large capital sums and incur high operational expenditure without achieving the desired amount of climatic control. There is therefore a great need for reliable prediction techniques to aid in the making of sound, informed decisions which will have a significant influence in the long term on the level of production costs. A computer program able to predict the heat flows and resultant climatic conditions on a long¬wall coalfaces has been developed. Throughout it's development underground measurements have been used to validate the computer model and it has been shown that for an advancing coalface under normal production conditions that the program predicts the climate to within 1°C of the measured conditions. This paper outlines a number of methods available to improve climatic conditions on longwall faces. The coalface temperature prediction program is used to quantify the effects of these methods on the climatic conditions for a model coalface and a comparison is given. In conclusion a cool¬ing strategy for longwall faces is outlined.

Jan 1, 1991

By P-M. Dupond, S. Lowrie, C. Tauziéde, Z. Pokryszka, A. D. Jones

A physical model has been developed to simulate the flows and mixing of gases in the waste of a longwall retreat coalface. The model is used in conjunction with computational modelling, and the distributions of permeability and gas emission in the model waste follow those in computer simulations (Pokryszka et al 1996). The physical model represents at 1170th scale a 200 m long, 3 m high coalface with a waste extending up to 280 m to the face start line. The model is tilted to the same seam slopes as the real face, e.g. 22° ascensional ventilation along the face and 7" slope to the dip. The purpose is to investigate the flow of three components: ventilation seepage flow through the waste; methane; and nitrogen injected to quell spontaneous combustion. A heavier-than-air surrogate gas (SF,) is used in place of methane, and therefore the model is inverted so that gas layers form along the 'roof". The main forces driving the flows in the waste (pressure gradients due to ventilation and the density difference of gas layers) are kept in proportion by appropriate scaling of the permeability. Calibration and validation used data from a coalface at a mine in the Lorraine coalfield. The model is now in operational use.

Jan 1, 1997

By V. Srajer

Several optimization approaches used by the Canadian mining industry were used to investigate surface coal mining operations in Canada. A computer program was applied to optimize truck/shovel systems and for various analyses. The analyses of eight western Canadian coal mines included investigation of fleet imbalance, under- and over trucking, development of the criteria for automated truck control, comparison study of various haulers and loaders, haulage layout, driving conditions, machine performance, servicing and maintenance policies, etc. Each property investigated supplied background information for the study and cooperated in optimization studies. The truck/shovel system optimization study is demonstrated as a test case to outline procedures and step-by-step instruction for similar applications.

Jan 1, 1989