Search Documents

By W. E. Cobb

The financial implications of environmental liabilities are becoming staggering, particularly for mining companies. The Environmental Protection Agency's (EPA) Record of Decision (ROD) list for Superfund mining sites has some pretty hefty financial commitments, such as the $10 million operable unit remedy for the Yak Tunnel at California Gulch (in Colorado) or the $40 to 60 million remediation at Bunker Hill (in Idaho). These costs are driven by the large volume and areal extent associated with historical waste management practices at mining sites. (It's difficult to have a low-cost remedy for a 20-square-mile site.) Unfortunately, there are other ways of generating environmental liabilities besides Superfund, such as non-compliance with Clean Air Act provisions, stormwater permits, or National Pollutant Discharge Elimination System (NPDES) permits. In the last 2 years, EPA has increased enforcement in its regulatory programs, which has resulted in increased fines and criminal actions. Leaders in other industries (primarily the chemical and manufacturing industries) are viewing environmental liabilities as a strong motivator to select engineering approaches carefully based on technical, legal, economic, and philosophical perspectives. Industry interest in waste minimization programs comes from the concept that it is economically advantageous not to create waste in the first place. Waste minimization programs typically balance increased front-end capital investment with the minimization of potential long-term environmental liabilities as a way to achieve the lowest total-or life-cycle-cost. A side benefit of waste minimization programs is that they tend to improve overall regulatory compliance. Waste management practices are also becoming philosophical, as evidenced by a May 11, 1992, Business Week article: Companies that incorporate innovative thinking on sustainable development will do more than clean up or prevent their own pollution. They'll make and distribute a product more efficiently than ever, worry about its lifelong environmental impact, plan for recycling, and get their suppliers on the bandwagon. This type of approach will require a new mind-set, new tools, and adjustments throughout the organization. A key aspect of waste minimization or life-cycle waste management programs is the incorporation of environmental costs into economic analyses that compare various waste management alternatives. However, the incorporation of environmental costs into an economic analysis can be more difficult than initially thought. As noted above, new tools-or even a new toolbag-are needed, such as new accounting methods that track and assign the true lifetime environmental costs of a particular product. One piece of the new toolbag is life-cycle cost analysis, which is discussed in this paper. To simplify the discussion, this paper looks at the total costs associated with a given mining site. The concepts presented in this paper, however, can be applied to any mine waste management decision. The ultimate extension of life-cycle costing, as presented in the Business Week article, is to include the potential environmental costs throughout the life of a metal. At this point, I am perplexed on why, let alone how, to include the potential downstream environmental costs (i.e., the costs associated with smelting, manufacturing, use, and recycle or disposal) throughout the life cycle of mined copper, lead, or zinc.

Jan 1, 1992

The response was good-one of the best the SAIMM has had to its various questionnaires. 231 replies were received from 2768 members representing a response of 8,35%. For fellows and Members together, the response was 13,7%. The spread of responses based on respondents' work situation appeared to be well balanced with some bias from those in consulting organizations. Members' perceptions of their employers' positions withrespect to environmental management looked somewhat optimistic, but it is encouraging to note that they reported that more than half were developing environmental management systems. Training of varying degree was taking place at al levels in their organizations. Members saw their Institute as an important agent inlifting environmental awareness, literacy and responsibility not only through the journal and symposia, but also by liaison with government departments and educational institutions. Most respondents saw environmental legislation both from local and overseas sources as affecting their organizations, their products and services with the emphasis on corporate image, core business and sales.

Jan 1, 1995

By J. F. Myers, F. M. Lewis

This second progress report of grinding presents comments regarding ball consumption and data pertaining to the hydroscillator, which is closed circuited with the tricone mill. A study and postulate of how balls function is presented. The paper summarizes cost reduction obtained by the method of "grinding for the tail race" rather than for "mesh tons."

Jan 11, 1950

By Michael J. Sapko, Kenneth L. Cashdollar

In This Chapter [Methane ignition as initiation source for much larger secondary coal dust explosions Rock dusting requirements to prevent coal dust explosions Dangers of hybrid mixtures of methane and coal dust] Although methane explosions are dangerous, those that involve coal dust are even more so. If exploding methane disperses and ignites the coal dust that has accumulated on the mine ribs and floor, the burning coal dust immeasurably increases the strength of the explosion. Such methane-dust explosions are prevented by inerting the coal dust in a way that prevents the exploding methane from igniting it. This chapter discusses the dust hazard and how it is pre-vented in U.S. coal mines. METHANE IGNITION AS INITIATION SOURCE FOR MUCH LARGER SECONDARY COAL DUST EXPLOSIONS The typical scenario for coal mine explosions starts with the ignition of a flammable methane-air atmosphere near the face. The turbulent winds from the primary methane explosion then disperse the coal dust. If there is insufficient rock dust (usually limestone), a secondary coal dust explosion then propagates throughout large sections of the mine. These scenarios have been studied extensively at the Bruceton Experimental Mine (BEM) and the Lake Lynn Experimental Mine (LLEM) of the NIOSH Pittsburgh Research Laboratory. The minimum quantity of methane required to initiate a coal dust explosion was studied in 1930 in the BEM [Rice et al. 1933; Nagy 1981] and then later in the LLEM, whose cross-sectional area (130 ft2) is over twice that of the BEM [Sapko et al. 1987a]. Studies conducted in the BEM closely simulated conditions that existed in operating mines in the early 20th century. The later tests in the 20-ft-wide entries of the LLEM simulated the geometries of modern mines with advanced roof support technology. The data from the BEM tests show that 13 ft3 was the minimum quantity of methane at the face that, when ignited, would disperse and ignite coal dust. In the BEM, this amount of methane was mixed with air to form a total flammable volume of about 140 ft3 of a 9% methane-in-air mix-ture. In the wider entries of the LLEM, about 37 ft3 of methane was required to disperse pure coal dust and start a self-sustained coal dust explosion. This amount of methane was mixed with

Jan 6, 2006

Coal washery wastes comprise tailings, finer than 0.5 to 0.1 mm depending on the sophistication of the washery, and coarse reject, typically finer than 50 mm. Subaerial disposal of coal tailings slurry at about 30 per cent solids by mass results in the formation of a delta with an average slope of about 1 in 100, representing one extreme. The ravelling of coarse reject on loose-dumping, results in an angle of repose slope with an angle of about 37o (1 in 1.3), representing the other extreme. The pumped co-disposal of coal tailings and coarse reject results in the formation of an upper delta with an average slope of about to one in ten, between the two extremes. The depositional behaviour of these three waste streams is discussed and compared in this paper. The important depositional and material parameters, and a theoretical description of the processes involved, are also presented. Comparisons are made between the depositional behaviour of the various coal washery waste streams, and natural depositional systems, such as rivers, alluvial fans, and scree slopes.

Jan 1, 1998

By Donald J. Keefe

The Remote Working Level Monitor (RWLM) is an instrument used to remotely monitor the Rn-daughter concentrations and the Working Level (WL). It is an ac powered, microprocessor based instrument which multiplexes two independent detector units to a single central processor unit (CPU). The CPU controls the actuation of the detector units and processes and outputs the data received from these remote detector units. The remote detector units are fully automated and require no manual operation once they are set up. They detect and separate the alpha emitters of RaA and RaC' as well as detecting the beta emitters of RaB and RaC. The resultant pulses from these detected radioisotope; are transmitted to the CPU for processing. The programmed microprocessor performs the mathematical manipulations necessary to output accurate Rn-daughter concentrations and the WL. A special subroutine within the program enables the RWLM to run and output a calibration procedure on command. The data resulting from this request can then be processed in a separate program on most computers capable of BASIC programming. The calibration program results in the derivation of coefficients and beta efficiencies which provides calibrated coefficients and beta efficiencies.

Jan 1, 1977

By Thomas J. Peters

In 1987, at the request of the U.S. Bureau of Land Management, the Bureau of Mines studied the 350-acre Henry?s Lake Wilderness Study Area (ID-035-077) in order to evaluate its identified mineral resources. The Wilderness Study Area is located in northern Fremont County, ID, approximately 140 air miles north-northeast of Pocatello and 3 miles south of the Montana border. The Wilderness Study Area is near the north shore of Henry's Lake at the foot of the southwest-facing slope of Black Mountain. Archean hornblende gneiss, the main rock type present, crops out northeast of the Madison Range Fault, which trends northwest across the southwest corner of the Wilderness Study Area.

Jan 1, 1988

By I. Perus, M. Fazarinc, G. Kugler, M. Tercelj

"Ledeburitic tool steels are highly alloyed steels used for specific highly loaded applications but are characterized by low and variable hot workability. In this contribution the importance of selecting the right choice of some essential process parameters, i.e. casting temperature, solidification rate and soaking temperature, needed for improving the intrinsic hot deformability of ledeburitic tool steels, is studied. An inappropriate selection of casting temperature and cooling rate results in precipitation of unusual eutectic carbides that decreases the hot workability, whereas with the selection of appropriate soaking temperature the temperature range of safe hot working can be broadened. For each initial as-cast microstructure individually determined soaking temperature should be selected.IntroductionThe surface cracking during hot deformation of ledeburitic tool steels reduces mechanical properties and their industrial yield. These tool steels have high hardness, wear resistance and high tempering resistance on one hand, and high flow stresses and low hot deformability on the other. Decreased hot deformability of the tool steels is attributed to the type, size, shape, distribution, fraction of eutectic carbides and/or other phases, grain growth, etc. at upper limit while precipitation of secondary carbides and decreased recrystallization rate at lower limit of the safe hot deformation temperature range, [1-6].The occurrence of cracks on most exposed areas of workpiece are related to the areas where similar conditions related to upper and/or lower limit of temperature working range prevail, i.e. areas with accelerated cooling, areas with higher value of accumulated strains where also decreased recrystallization rate with simultaneously presence of higher tensile stresses takes place, furthermore areas of workpiece which are due to combustion conditions in furnace heated to higher temperatures, etc. Thus the areas, where combination of previously mentioned conditions prevails, are more exposed to cracking. This additionally requires that hot deformability of ledeburitic tool steel should be considered as a complex problem. Publications in the literature with regards to hot deformability of tool steels are predominately of a partial nature thus all reasons for unexpected occurrence of cracks are not sufficiently explained in available literature so far. Furthermore modern practice proves that previous processing parameters significantly influence the hot deformability and thus this cannot be considered as a constant value. During heating, soaking and hot deformation various processes take place: decay (decomposition) of carbides, formation of new carbides, dissolution of carbides and of alloying elements, etc. Thus depending on variation of process parameters and chemical composition, that consequently influences the processes related to carbides, shifting of decreased deformability at both limits of temperature working range to higher and/or to lower temperatures can occur, [1-14]."

Jan 1, 2012

By C. E. Wethered

THE Morning mine is operated through one main working adit, known as No. 6 or 800 tunnel level. At a distance of 10,000 ft. underground from the portal is the vertical four-compartment, main working shaft, which extends to the 3050 level, a distance of 2250 ft. below the collar, or 800 level. Shaft-stations are cut and levels opened every 200 ft. of depth and the ore is stoped to the next level above. The vein is nearly vertical and the ore is usually fairly massive and brittle. Both walls are soft and slabby and much difficulty is therefore experienced in holding them. Stopes are usually carried up in short sections, approximately 200 ft. in length, that are mined as rapidly as possible in order to avoid a too great replacement or repair of stope timbers. The four-compartment vertical shaft, 110 ft. in the footwall of the vein, is the sole medium of outlet for all ore mined below the adit level. Two compartments of this shaft are used exclusively for hoisting ore, except at the time of changing shifts, when one compartment is used to handle some of the men and timber. The third compartment is equipped for handling men, tim-ber and all general supplies and is operated by a Nord-berg 300-hp. electric hoist. This hoist has a lifting ca-pacity of 14,000 lb. with an average rope speed of 800 ft. per minute. The fourth compartment is used solely as a manway and pipeway.

Jan 7, 1927

By K. Whysner

The recycling of metal resources in mining influenced water (MIW) requires a paradigm shift from within the mine water treatment industry. The potential to recover zinc for beneficial use in the micronutrient fertilizer industry was investigated through a survey of zinc micronutrient fertilizer representatives. An application of the findings to a case study of the Argo Tunnel influent MIW was then implemented. It was concluded that the potential to beneficially reuse MIW residuals in fertilizers exists; the current process sequences of treatment will need to be modified if metal recycling is to be prioritized.

Feb 27, 2013

By James T. Gow, Oscar E. Harder, Anton de S. Brasunas

This paper deals with the results obtained and the techniques employed in determining: 1. Liquidus and solidus temperatures of the HH and HT type heat-resistant alloys. 2. The relation of true temperatures (thermocouple) to apparent temperatures (optical pyrometer) for the molten HH and HT type alloys. This work was the outgrowth of needing to know something definite about these temperatures in order to study the effect of pouring temperatures, shake-out times, and heat-treatments on the properties of some heat-resistant alloys. The information developed is thought to be of interest to industry for guidance in foundry practices and the industrial heat applications of the alloys. This paper is based upon work that has been done for the Alloy Casting Institute at Battellc Memorial Institute. Liquidus and Solidus Temperatures of HH and HT Type Alloys Experimenta1 Procedures Temperature-time curves were obtained during the cooling and solidification of several HH and HT type alloys. The metal was melted in an Ajax high-frequency, induction furnace and poured into a core-sand mold for cooling. The temperature measurements were obtained by means of a platinum, platinum-rhodium thermocouple contained within a fused silica sheath, which was extended through the side wall of the dry core-sand mold to a point at about the center of the mold cavity, which was 3 in. in diameter by 5 in. deep. The cold junction of the thermocouple was kept in an ice bottle, and the temperature was recorded automatically on a direct-reading potentiometer recorder. Through a switching arrangement, the temperature recorded was checked occasionally with a portable Leeds and North-rup potentiometer indicator. Less than a 5°F. variation in the two instruments was always found. This is within the limit of accuracy of readings. The thermocouple used was checked for accuracy against a standard couple, both before use on this work and after completion of the work, by the instrument laboratory. Temperature-time Cooling Curves Fig. I is an enlarged reproduction of a part of one of the cooling curves over the temperature range of 2600' to 2200°F. for an alloy of the HT type with 0.45 per cent carbon, 16 per cent chromium, and 36 per cent nickel. This is a typically shaped cooling curve as obtained for the alloys. It will be noted that two temperatures "re shown on Fig. I for the liquidus temperature. It is thought likely that the higher temperature, A, at the point at

Jan 1, 1945

By J. B. Gayle

The merits of the various methods for dry-quenching coke have been the subject of numerous publications and almost equally numerous controversies for the past 40 years.5/ Most investigators have concluded that dry quenching is advantageous. Some have based their arguments on the improved physical properties of the resultant cokes. Others have claimed little or no improvement and have based their arguments on the economies acquired from the recovery and utilization of sensible heat. The extent to which the method of quenching influences the properties of the resultant cokes is of importance in connection with the operation of both commercial and experimental ovens. On the other hand, the recovery and utilization of sensible heat are economic problems related solely to commercial oven operation and- depend on the method of dry quenching used and the demand for a low intensity energy source. The scope of the present Bureau of Mines investigation has been limited to a comparative study of the properties of wet- and dry-quenched cokes produced from six coals and blends carbonized at flue temperatures of 2, 000° and 2,400° F. in the Tuscaloosa oven.

Jan 1, 1959

By I. Filzwieser, S. Wallner, M. B. Hanel, A. Filzwieser

Whenever thinking about increasing tankhouse performance two major aspects has to be considered, the technological feasibility as well as the economical impact. For meeting the requirement of an increased current density leading to an increased productivity, Mettop has developed the METTOP-BRX Technology, which allows the introduction of fresh electrolyte between each pair of anode and cathode. As an example of a green field approach the installation at Xiangguang Copper Co., Ltd will be described. Since the start up in 2011, Xiangguang Copper Co., Ltd operates one of their two copper refining tankhouse with a current density of 420 A/m2 and a current efficiency above 98% in average. At Montanwerke Brixlegg Ag, as an example of a brownfield installation, the annual production could be increased by 50%. Although for many years a total of two industrial applications are in operation, the successful implementation of this technology that result in significant operational and economic advantages has not been fully accepted within the industry due to misunderstandings, incorrect interpretations and lack of awareness. It is intended with this paper to create a better understanding about the parallel flow technology and help to eliminate worries and concerns.

Mar 1, 2017

By A. Schaum

On average, there are approximately 10 fatal haul truck accidents per year. The most common causes for haul truck accidents include mechanical problems, inadequate training and insufficient road/berm maintenance. Due to the frequency and magnitude of haul truck accidents, new training methods are being investigated. With the widespread availability of computers and new technology becoming more reasonably priced, the ability to incorporate computer-based training for miners is becoming more possible. It has been shown that computer-based training is just as effective in knowledge acquisition as traditional lectures, and computer-based training can lead to a significant increase in the retention of material (Williams and Zahed, 1996). Studies have also shown that more engaging training methods lead to more effective knowledge acquisition (Burke et al., 2006). A supplemental system for current and new miner training to address the common causes of fatal accidents was developed. The training system is a virtual preshift inspection of a haul truck, and it can train new haul truck operators to identify parts that look defective. The training will increase an operator?s ability to recognize problematic parts and correctly identify the corrective action needed. Increasing the quality of training by providing an engaging, simulated hands-on environment will lead to safer behaviors by trainees, which will ultimately lead to fewer accidents and fatalities.

Jan 1, 2008

By J. Dilbeck, J. K. Ratliff, T. Petrov, Z. Brown

"In efforts to improve dust control during deep cut continuous mining a supplemental atomizing spray system, mounted on 14CM15 continuous miner, has been designed and successfully implemented in a U.S. coal mine. The mine is 2.1 m (7-ft) high and uses a blowing curtain face ventilation system with 1.1 m (3.5-ft) curtain offset from the rib. The face ventilation design parameters were set to 9.4 m3/s (20,000-cfm); 4.2 m3/s (9,000-cfm) line curtain flow rate, and 3.8 m3/s (8,000-cfm) scrubber capacity. The performed in-mine measurements, before and after the implementation of the atomizing spray system, showed a significant decrease in the respirable dust levels at the operator place as well as at the return. The paper describes the supplemental water spray system design and performance supported by three-dimensional computational fluid dynamics (CFD) simulations and in-mine test data.INTRODUCTIONThe work on this project have started in 2015 with a study of the conventionally applied face ventilation layouts. The specific behaviour of the face ventilation system have been analyzed trough in-mine measurements and computer modeling of typical cut scenarios. An computer modeling methodology have been developed for estimation the respirable dust concentration (RDC) using tracer gas to RDC contour mapping, calibrated by a single point value, provided by in-mine measurement. Utilizing the results of this study the engineering staff of the mine designed and implemented a supplemental atomizing spray system to improve the dust control during the deep cut continuous mining. Today the atomized spray system is successfully applied demonstrating steady performance and a significant decrease in respirable dust concentration on the working places of the continuous miner (CM) and coal transporters (CT) operators as well as at the return air stream. Information about the applied type of spray nozzles provided by other researchers (Cheng, 1973; Dick et al., 1996; Organiscak & Page, 1998; Pollock & Organiscak, 2007) and spray system manufacturers (Spraying System Co, 2011–2018; Steinen Mfg., 2016) have been used in this project. CFD code and simulation approach validated in a study conducted in 2000-2014 have been applied (Turner et al., 2002; Wala et al., 2004, 2007; Petrov, 2014)."

Jan 1, 2019

By Choon K. Quan

Subsidence is a surface manifestation of the underground development and exploitation of minerals, and its impact on the environment is becoming of increased concern, particularly in the face of an accelerating demand for energy and minerals. In the United States, the state-of-the-art in subsidence prediction, control, and prevention and in subsidence-related damage abatement has not progressed to the level achieved in other countries. To bridge this gap, the Bureau of Mines, through its Mining Environmental Research program, is pursuing a comprehensive subsidence investigation, specifically designed to address major problems on the local, regional, and national level.

Jan 1, 1979

By T. M. Morris

The forces acting between a small rod, one end of which was made water repellent, adhering to a much larger air bubble in water were measured. An equation is deduced which correlates these forces and the influence of each force is discussed. The importance of the size of bubbles in a flotation cell is emphasized.

Jan 1, 1950

By McAuliffe, Eugene

THE TERM "engineer" has been defined in many ways by many men broadly speaking the statement that "an engineer is one versed in or practicing any brar1c.h of engineering" is sufficient. A rather close relation exists between the sciences of surgery and engineering. A successful surgeon must have the capacity to perform the most delicate work, under extremely circumscribed conditions. This portion of his education is purely mechanical and although marvellous in itself, it must remain secondary to that greater possession, a thorough knowledge of human anatomy coupled with a comprehensive understanding of human psychology. In sub- stance, the surgeon must not only know how to operate but what is more important, he must be able to decide when, if ever, the operation should be undertaken.

Jan 1, 1932

By G R. Hancock, W D. D P Welivitiya

is placed in a waste rock dump, which is usually later reshaped to be erosionally stable, initiate and sustain vegetation and ultimately integrate with the surrounding undisturbed landscape. However, it is unclear how this exhumed material will weather and evolve for most sites. Also, there is a lack of data on the weathering of post-mining materials. If weathering is better understood, then there is the potential to improve rehabilitation outcomes. To improve predictions of the evolution of soil properties and weathering-limited erosion, estimating the rate at which fine, transportable material is produced from the weathering of larger, non-transportable particles and the resultant fragment size distribution and how that distribution evolves over time is necessary. This study examines the weathering process for four different coalmine waste rock materials for a Bowen Basin, Queensland site. Materials obtained from various areas of the coalmine were subjected to cyclic wetting and drying and heating and cooling. Particle size distribution and other material properties were explored after each experimental cycle to ascertain how the material changes during the experimental cycles. The particle size distribution data of wet and dry cycles were used as input data in a numerical weathering model to explore the dynamics of the weathering process for each material sample. A Monte Carlo framework was employed to assess the geometry of the weathering products, weathering rate and the number of daughter particles produced within a weathering cycle. Then the SSSPAM Landscape Evolution Model was used to evaluate the influence of weathering on erosion and landscape evolution of a post mining landform. SSSPAM simulations with: (i) active weathering and (ii) without weathering were run for each material. The erosion rate and the overall landform structure were then compared between weathering and non-weathering simulations.

Aug 2, 2023

By A. Shemi

Tungsten carbide scrap (WC–Co) is material generated from the tungsten carbide manufacturing process and worn out or used carbide parts from industry. Tungsten (W) ores contain about 3 wt% WO3 and their W concentrates about 10– 75 wt% WO3. Tungsten carbide scrap typically contains 40–95 wt% W. The high intrinsic value of W and the fact that the least valuable scrap contains more W than the average tungsten ore makes tungsten carbide scrap a worthy material for re-use. This study has investigated the selective dissolution of the cobalt (Co) binder phase, and recovery of tungsten monocarbide (WC) and Co using an acid leach process. The Co component was selectively leached leaving the WC solid particles intact. Further investigation using a complexing agent-aided acid leach process that takes advantage of organic chelating agents that form a soluble tungsten complex in place of the passive insoluble tungsten oxide is envisaged. The optimal dissolution of the Co binder phase using an inorganic acid in conjunction with an organic complexing agent is a novel approach with the potential of reduced leaching times and possibility of regenerating the unreacted organic acid.