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By J. Noll, J. A. Organiscak, A. B. Cecala

"In recent years, significant strides have been made to optimize the design of filtration and pressurization systems used on enclosed cabs of mobile mining equipment to reduce respirable dust and other contaminants and provide the best air quality to the equipment operators. This synergetic effort has involved original equipment manufacturers building mining equipment, manufacturers of heating, ventilation, and air conditioning systems for mobile equipment, filtration and pressurization system manufacturing companies, as well as the National Institute for Occupational Safety and Health, and other government organizations. Considering all the advances made in this area over the last decade, one aspect that NIOSH still needs to assess is the longevity of optimal cab performance with respect to the quality (filtering efficiency) of the filters used in filtration and pressurization systems. In today’s culture, most health and safety professionals automatically believe that HEPA quality filters need to be used to provide the greatest level of protection to workers. Researchers at the Office of Mine Safety and Health Research for NIOSH hypothesized that HEPA quality filters may not be optimal for the mining industry and speculated that MERV 16 rated filters would be more appropriate in most cases. In order to test this hypothesis, NIOSH performed a two-year study comparing both HEPA and MERV 16 quality filters on two pieces of underground limestone mining equipment, being a roof-bolter and face drill machine. Testing showed at the 95 pct. confidence level that there was no statistical difference between the two efficiency filters on both pieces of mining equipment. Since the MERV 16 rated filters were less restrictive and provided greater cab pressure, and since they did not have to be replaced as often as the HEPA quality filters, researchers concluded the MERV 16 filters were the optimal choice for both pieces of mining equipment in this case study comparative analysis. INTRODUCTION When most health and safety professionals today think about filtration efficiencies and their correlation with protecting workers’ health, the normal assumption is the higher the efficiency of a filter, the greater the protection afforded to the workers. The next logical step is to believe that HEPA filters deliver the greatest protection for workers because they provide the highest filtering efficiency. Obviously high-efficiency intake filters are a necessity for an effective cab filtration and pressurization system on mobile mining equipment, but what is the optimal filter efficiency rating for achieving high levels of cab protection factor performance over the service life of filters? To address this question, the National Institute for Occupational Safety and Health (NIOSH) has performed an in-depth laboratory research study over the years simultaneously with numerous field studies to retrofit used enclosed cabs on mobile mining equipment with newer and more effective filtration and pressurization systems."

Jan 1, 2016

By E. J. Wade

My subject is gold price forecasting and monitoring as an important aspect of gold marketing. While I 'm specifically addressing gold, it is understandable that many other commodities could be readily substituted. Gold marketing must be studied as three distinct processes, and it is my intention to cover each of these processes in turn. First I?ll cover the process of gold price monitoring and forecasting in some detail. In order to select a method, or combination of methods, to be used to sell gold a determination of the future price profile is essential. The profitability of the sales effort will be determined, to a large extent, by how accurately the future price behavior of the gold market has been forecast.

Jan 1, 1985

By C. A. Summers

The U.S. Bureau of Mines applied process mineralogy to investigate a lead and zinc deposit located near Story Creek, Colville Mining District, Alaska. Mineralization is hosted by the Kayak Shale in veins, veinlets, and breccia. Sphalerite and galena, with supergene anglesite, occur in symmetrical quartz veins and between breccia clasts. The study sample analyzed 2.11 percent Pb, 5.37 percent Zn, 0.014 percent Cu, and 1.2 oz/ton Ag. Analyses of crushed products showed that 33 percent of the sample weight, and more than 50 percent of the Pb and 65 percent of the Zn, are in the minus 850 µ m fraction. Liberated grains of sphalerite and galena were found in crushed products finer than 300 µ m. Beneficiation tests indicate the material is amenable to processing by traditional gravity and flotation techniques.

Jan 1, 1993

By Hun-Joon Sohn

Chemical metathesis and electrochemical reductive conversion of chalcopyrite in the presence of cupric ions were studied in sulfuric acid solutions for temperatures up to 90°C. The process results in the displacement of iron in the chalcopyrite lattice by copper ions with rejection of ferrous ions to the aqueous phase. The rate of reaction was found to be very slow, requiring subsieve-sized particles for extensive reaction to occur. The reaction was insensitive to copper ion concentration. Stirred ball milling of chalcopyrite introduces lattice strain. The reaction rate with strained particles was markedly higher than with annealed chalcopyrite. The reaction rate was found to be diffusion-limited, showing two distinct reaction stages corresponding to the formation of CuS (covellite) followed by Cu1.8S (digenite). The experimental activation energy for the first stage was 102 J (24.4 kcal) and the second stage 123 3 (29.4 -kcal) per mole. The rate-controlling process is diffusion of lattice ions, probably iron. The enhanced rate after milling is attributed to a recrystallization process which provides new paths for diffusion along dislocations and grain boundaries.

Jan 1, 1984

By O. H. Rostad

The importance of geology in ore reserve estimation has been stated by several authors. King et, a1 (1982) reported that the geological factor was the key deficiency where serious weaknesses in ore reserve estimation appeared, especially in grade. The foundation for a successful mining operation is an ore reserve estimate that neither overstates nor understates the true situation as to tonnage and grade. Overestimation of reserves can have devastating economic results. Overestimation of tonnage may lead to wasting money on an overbuilt plant or worse yet, if grade is seriously overestimated also, to undertaking an operation that is doomed to economic failure from the outset. Understated ore reserves can result in building a plant that is smaller than optimum which may result in higher unit costs. At worst, understated tonnage of ore reserves can result in a missed opportunity for a profitable operation. Failure of the ore reserve estimator to properly take into account all geologic and allied factors pertaining to the deposit can result in an ore reserve estimate that is overstated either as to tonnage or grade or both. This paper will focus on these factors and will not discuss rules about distances above or below a drift that should be given a classification of proven or probable, etc. Each deposit has its own particular characteristics which often require modification of general rules for defining limits of proven and probable ore blocks that work satisfactorily in another deposit. A number of references are included which discuss some of these problems. Definitions of ore reserve classifications and an illustration are given in the Appendix.

Jan 1, 1985

By C. L. Karr

Researchers at the University of Alabama are investigating artificial intelligence based computer models of mineral processing systems. Two approaches have been found to be particularly effective in developing data-driven computer models. The first approach employs neural networks which are computational paradigms based on the mechanics of the human brain. They are able to extract the basic relationships between input and output variables from large data sets. The second approach combines fuzzy mathematics with genetic algorithms to produce an adaptive modeling system. Fuzzy mathematics provide computers with the capability of manipulating abstract concepts like those which humans use so effectively in decision making. Genetic algorithms are search algorithms that mimic evolutionary processes apparent in nature. Together, these two techniques can be used to produce an effective modeling system. In this paper, the two approaches to modeling are compared and contrasted with respect to accuracy and computational time while used to model three mineral processing systems: (1) a grinding circuit, (2) a hydrocyclone separator, and (3) a flotation circuit.

Jan 1, 1997

By R. A. Allwes

In-plane bending and torsion tests were conducted on full-scale masonry walls to evaluate three post-reinforcement designs. The designs were developed to minimize longwall mine subsidence damage to existing residential masonry foundations. The bending tests show that vertical and horizontal post tensioned tendons significantly increase the resistance of a masonry wall' to in-plane bending. The torsion tests reveal that post tensioned tendons increase a masonry wall's limit of deformation but do not increase its torsional stiffness. The torsion tests also show that the masonry units minimally contribute to the torsional stiffness of a masonry wall.

Jan 1, 1995

By Frank A. Jerabek

Pneumatic stowing was first introduced in longwall mining in the middle twenties. Since that time it has advanced through many stages of development, particularly abroad, which have greatly improved its efficiency and contributed to its growing use. Pneumatic stowing originated in coal mining but has also been adopted in metal mining. This paper discusses the techniques of pneumatic conveying of. stowing material and equipment and applications of pneumatic stowing.

Jan 1, 1966

By Hans von Michaelis

The renaissance in extractive metallurgical practices for gold and silver recovery is far from over. This is one conclusion of a three year investigation into innovations in Cold & Silver Recovery by Randol International Ltd. (1981, 1983). The six volume reference report reviews a host of new processes and innovative applications of older metallurgical practices. Some of these were summarized by von Michaelis (1982, 1982a). There are several reasons to expect this renaissance to continue. One reason is the nature of gold and silver deposits. The list of known occurrences of These metals is very extensive. There are literally tens of thousands of prospects but over 99% of these are too low grade, too small or too refractory for a viable operation employing conventional processing.

Jan 1, 1983

By Richard G. Almes

Since the failure of a major coal refuse disposal embankment and impoundment in the Buffalo Creek watershed near Man, West Virginia in early 1972, there have been extensive changes in the design and construction requirements for coal refuse disposal facilities located throughout the United States. The primary emphasis has been on improving the safety of these facilities, particularly for impoundments which are capable of storing millions of gallons of process water and storm runoff. The Mine Safety and Health Administration (MSHA) of the U.S. Department of Labor (formerly the Mining Enforcement and Safety Administration, U.S. Department of interior) has been the lead federal agency in promulgating regulations pertaining to coal waste disposal. In 1974 and 1975, studies were undertaken by our firm under contract to the Mining Enforcement and Safety Administration to prepare a comprehensive engineering and design manual to be used by operators and engineers in the planning and design of coal refuse disposal facilities with the intent ion of avoiding any more Buffalo Creek failures. The resultant 800-page document addresses major subjects such as safety, environmental controls, and cost. Specific topics include characterization of coal refuse, classification of disposal facilities, project planning, geotechnical investigations, testing and design requirements, hydraulic and hydrologic design, environmental factors, operations, and monitoring, instrumentation, and maintenance.

Jan 1, 1980

By A. C. Barlow

The use of deep wells for waste disposal is not a new technique. The production phase of the oil industry has been using this method to dispose of unwanted oil field brine since the 1930's The adoption of this method by other branches of industry, however, to dispose of manufactured wastes is a relatively new development, but one which is finding increased use (2). Deep well waste disposal is not an ordinary technique even though it is finding relatively wide application. In fact, just the opposite is true; it is still a rather extraordinary measure. It is not now, nor is it ever likely to be a disposal method which can be assured of success before it is tried.

Jan 1, 1964

By I. Iwasaki

The effects of autogenous grinding and conventional grinding on the floatabilities of copper-nickel sulfides were investigated as a part of a pilot-plant development project on the differential flotation of Duluth gabbro. At the same mesh-of-grind copper, nickel, and cobalt recoveries were higher and residual sulfur in the flotation tailings was lower with the autogenously-ground pulps. With the ball-mill-ground pulps the residual sulfur in the tailings could not be lowered to the level attained by the autogenously-ground pulps even at increased levels of the collector addition. From mineralogical examinations of concentrate and tailings samples, an electrochemical interaction between grinding media and sulfide minerals was thought to have a greater effect on sulfide mineral flotation behavior than the breakage characteristics of the ore samples in these two types of mills.

Jan 1, 1981

By Vishnu S. Gupta

A modular computer program APEX (AMAX Process Evaluation Executive), has been developed at AMAX Extractive R&D, Golden, Colorado to facilitate rapid simulation of steady state material and energy balances of existing and/or proposed metallurgical process flowsheets. Currently, APEX is being used for the design, analysis, and evaluation of several of AMAX?s Nickel, Molybdenumand Tungsten processes. A unique feature of APEX is that it allows specifications of flow rates and compositions for different solid size fractions in addition to aqueous organic and gaseous phases. Thus, a metallurgical process which may involve crushing, grinding, flotation, leaching, washing, solvent extraction, precitation and refining operations can be simulated in a single computer run using APEX. APEX requires two input data files. The first is a process data file which includes physical and thermodynamic properties of the various chemical components of interest. This data file is unique to the process under study and does not require changes for alterations in the process flowsheet. The second data file is specific to a simulation case and includes descriptions of the flowsheet, various feed streams and the process equipment's operating conditions. In addition to temperature, pressure and percent solids, calculated information for each stream includes weight and volumetric flow rates, chemical compositions, specific gravities and enthalpies of solid, liquid and gas phases. For each process equipment in the flowsheet, APEX prints its operating conditions and detailed information about the streams that enter and leave the unit. Models of several general unit operations are preprogrammed in APEX. Also, the modular design of APEX permits quick and easy additions of simulation models which are specific to new and/or unique process operations. To study process stability and optimization, APEX permits several cases of a flow-sheet to be run together. Three simulations of the Moa Bay Nickel process have been excluded to illustrate the ease and flexibility of using the APEX system.

Jan 1, 1980

By N. C. Miller

In situ stope leaching is an innovative mining system that reduces the surface impacts of conventional underground mining. As in any leaching operation, stope leaching requires hydrologic site characterization and control of leaching solutions. Several tracer tests, using sodium chloride (NaCl) in various concentrations, were conducted by the U. S. Bureau of Mines (USBM) in an underground experimental stope to simulate a leaching environment. The tests were conducted in fractured crystalline rock that was partially saturated. As tests progressed, the surrounding fractures became more saturated. A predominant flow direction away from the stope was found during testing. Testing procedures, preliminary results, and remediation ideas based on field observations are presented in this paper.

Jan 1, 1995

By E. R. Bauer

The trend in underground room-and-pillar coal mining is to employ remote-control continuous mining machines and extended cuts, 12 m (40 ft) deep or more. This system of coal extraction, adopted by over 435 mines, can create additional worker-safety hazards. To address the ground control and worker-positioning hazards, a combination of statistical analyses and numerical modeling was conducted. Initially, the reported roof-fall incidents and fatalities were reviewed to delineate the ground-control hazards. Then, the application of the Coal Mine Roof Rating (CMRR) for estimating safe extended-cut depths was evaluated. Finally, computer modeling to predict roof displacements during extended-cut mining was completed. The paper describes the results of these studies and their impact on the safety of extended-cut mining.

Jan 1, 1999

By Y. H. C. Wang

A detailed study of carrier flotation of kaolin clay using calcite showed the major beneficiation mechanism to be enhanced aggregation between anatase and calcite under intense agitation conditions. In order to develop an understanding of this selective aggregation, surface charge characteristics of kaolinite, anatase and calcite were studied under simulated flotation conditions. Zeta potential of all these minerals tended towards a constant negative value in ole- ate solutions under certain conditions possibly due to adsorption or precipitation of oleate on them. However, whereas the zeta potential of anatase in the oleate solutions was not influenced by the agitation level, that of kaolinite was found to be strongly dependent on the agitation intensity. The effect of oleate on zeta potential of kaolinite was reduced by an increase in agitation intensity. It is suggested that oleate is much more firmly bound to the surface of the anatase and that this preferential attachment is responsible for the enhanced selective aggregation of the anatase with calcite. Agitation level plays a major role in carrier flotation since intense agitation is considered to en- hance both the chemisorption of oleate on anatase and preferential detachment of calcium oleate precipitate from the kaolinite surface, all of this producing a large difference in the surface properties of anatase and kaolinite, and hence in their tendency to aggregate with calcite.

Jan 1, 1981

By Klaus Grebe

Recent investigations by Mannesmann Research have shown that disintegration of sinter with widely varying quality levels is subject to a much more complex set of influences than was previously assumed. It was confirmed that disintegration at temperatures between 300 and 600 °C is triggered by the degradation of hematite. The specific tendency of hematite to disintegrate is, however, not constant: sinters containing the same amount of hematite can show widely differing disintegration tendencies depending upon structural homogeneity, porosity and gangue quantity. Especially sinters with heterogeneous structures transmit stress to the hematite phase and this favours disintegration. Another factor is the brittleness of the glassy silicate phase, which can be influenced even by small modifications of minor gangue constituents.

Jan 1, 1981

By Sadatoshi Ohmori, Karen Shinoda, Nobuharu Isago

Method of tunnel excavation is generally classified such as full-face excavation, bench-cut excavation, diaphragm with center pillar excavation, center drift advancing excavation and so on. These excavation methods should be selected properly in terms of ground condition, the area of tunnel section, the arrangement of construction. Center drift advancing excavation method in mountain tunnel construction, is often applied under quite weak ground condition, prior to the main tunnel widening excavation. Recently, the advancing drift is for the excavation of extreme larger section in main tunnel to confirm the stability of face. In addition, we make advancing deformation occur in drift when the construction was done in poor ground like squeezing and swelling ground, and the force occurred in main tunnel was expected to reduce by the effect of ‘dodging’ for support structure. Mechanical relation between drift and main tunnel has been mainly grasped on past experiences in Japan. However, the characteristic of tunnel enlargement was partially discussed by using the three dimensional analysis and the result was grasped by past experiences on the basis of each tunnel construction. It is considered that the natural ground stress is normally released as the advance displacement, but it was released after the main tunnel widening, causing a displacement and deformation increase. Up to now, the construction practice has shown the reduced displacement during the main tunnel widening excavation by the drift, and the numerical analysis agreed with above observation. However, there is no report found that the displacement and deformation at the time of widening excavation of the main tunnel become larger in case of a drift application. In Kyusyu area, western part of Japan, the northern part of Yoshinomoto tunnel was applied an advancing bench-cutting method for a center drift for the purpose of obtaining the geological information for support selection of the main tunnel in widening excavation. The shape of center drift was a perfect circle with a diameter of 4.0 m or 6.0 m and the same temporary support regardless of the geological situation. As a result, the displacement and deformation of the main tunnel after widening excavation were larger than the section where the center drift was not applied. Furthermore, the displacement and deformation of the main tunnel after its widening excavation was considered larger in the section where the cross-section of the center drift with 4.0 m diameter was applied than one with 6.0 m. Therefore, the center drift with a high rigidity support structure had the effect of suppressing the advancing deformation prior to the main tunnel widening excavation.

Jun 13, 2021

By Bernard L. Merlo

INTRODUCTION Modern mine management is constantly striving to develop improved mining methods which will not only increase productivity, but will also provide a safer work environment and make the most efficient use of our natural resources. Progress can be seen in this area by tracing mining methods through history. Work that was originally done with hand tools progressed with the age of mechanization to conventional mining, matured to continuous and longwall mining, and the advent of short¬wall mining, a combination of continuous and longwall, has recently been seen. This new method of shortwall mining provides a promising method for safe and ex¬pedient coal extraction. This study focuses upon the planning, design de¬velopment, and operation of the first producing short¬wall unit in the US which was operated in the Pittsburgh coal seam in northern West Virginia. MINE DESCRIPTION The mine is located in northern West Virginia at Grant Town in the heart of the high volatile Pittsburgh coal seam. Originally opened in 1901, the mine has be¬come one of the largest in the US, encompassing an area of approximately 103.6 sq km (40 sq miles). The seam being mined was the high volatile Pittsburgh seam which ranged in thickness from 1.8 to 2.96 m (6 to 91/2 ft). Three types of mining methods were employed: con¬tinuous mining, longwalling, and shortwalling, with each type accounting for 50%, 30%, and 20% of total pro¬duction, respectively. A total of 630 contract and super¬visory personnel were employed to produce the mine's designed annual tonnage of 1.8 Mt (2 million st). There were ten producing sections, eight continuous miners, one longwall, and one shortwall, operating a total of 22 unit shifts per day. Eight shafts, varying in depth from 80.2 to 194.2 m (263 to 637 ft) provided entrance to the Pittsburgh coal seam. These shafts were used for ventilation, portaling, coal hoisting, supply, and emergency escape hoisting. Ventilation was achieved by means of three exhaust fans which provided 707.9 m3/s (1.5 million cfm) of air to the mine and removed approximately 141 584 m3 (5 mil¬lion cu ft) of methane per 24 hr period. The room-and-pillar method was used for secondary recovery with designed barrier blocks between panels of 61 m (200 ft) in width. A double row of blocks was left around each gob area to provide efficient bleeder action

Jan 1, 1982

By William J. Shampine

The Floridan aquifer, which underlies all of Florida, yields water with a sulfate content of less than 50 parts per million in the north-western part and throughout most of the center of the State. In the southern part of Florida and along the most of the east coast, the sulfate concentration generally exceeds 100 parts per million and is as much as 1,700 parts per million. The sulfate concentration tends to be higher in the deeper zones of the aquifer. This map shows the sulfate concentration in the upper part of the aquifer. Sulfate is found in almost all natural water. Sulfate in rainwater is dissolved from impurities and gases in the atmosphere. Rankama and Sahama (1955, p. 314) report that the average sulfate content of rainwater is two parts per million; however, concentrations have been as high as 283 parts per million. Much of the sulfate in rainwater comes from hydrogen sulfide gas which is generated in shallow water on the continental shelves. The combustion of bituminous coal used for heating and industrial purposes seems to be an important local source of sulfate.

Jan 1, 1966