Search Documents

By T. Faulkner, S. A. Richards

"Classic engineering economics provides the mining engineer with a fundamental approach to choosing between capital spending alternatives. This approach has been heavily used over the years and is an accepted technique for most investment decisions. There is a shortcoming that I have run into over the 15 year period when I worked in business planning roles. The classic time value of money approaches such as Net Present Value, Return on Investment, and Internal Rate of Return provide good estimates, but the input assumptions may fall short of describing the real material differences required by these analysis techniques. If the cost benefit analysis is defined solely on the improvement of the item being replaced or improved, the true profitability of the decision may be overestimated. Productivity improvement based capital projects can yield more accurate forecasts when conducted in concert with a “bottleneck analysis”. INTRODUCTION A review of the Theory of Constraints, (Goldratt, Cox, 1984) Lean, (Womack, 2003) (Rattner, 2006) and Six Sigma (Cryger, DeFeo 2015) lead us to recognize that these process improvement methodologies are oriented to the manufacturing process. These systems generally involve a factory that the material moves through on the way to becoming a final product. The mining challenge has many similarities to manufacturing once the ore has been won and made ready for processing. Before that point, however, the process is somewhat inverted while the ore is being won. Instead of the material moving through the factory, the factory is moving through the material. The Theory of Constraints (TOC) was used in an underground context by Baafi, Cai and Porter at 2015 APCOM, but even this groups’ analysis did not carry the concept from mining to shipping of the final product. There can be spatially distributed data that can affect the mining throughput constraints, some of which can be determined from exploration results. Identifying constraints can lead us to mapping productivity bottlenecks on future mining. Knowing this may improve decision making by eliminating one of Jim Fishbein’s three deadly sins of strategic planning: incomplete planning. When evaluating capital investment alternatives you should evaluate the impact of any proposed improvements on the entire operation. At the core of any mining system is the materials handling system. This can be typically expressed as the system that handles the raw material from the “face” through processing and then handling the finished product as well as the waste material. A “Bottleneck Analysis” is an investigation into the factors limiting a material handling system’s productivity (Goldratt, Cox, 1984). Mining material handling systems are usually composed of several linked components such as draglines, shovels, loaders, hydraulic excavators, continuous miners, longwalls, highwall miners, bucket wheel excavators, LHDs, feeders, conveyor belts, stockpiles, crushers, processing plants with various circuits, and waste handling systems. Each of the aforementioned components has a slightly different throughput capacity. When these are linked in series, the one with the lowest throughput capacity limits all of the others, creating the bottleneck for the system. Every material handling system has a bottleneck. In the mining environment, a subtle, but very significant phenomenon may also occur. The bottleneck may change as a result of a change in the raw feed qualities, face recession, overburden depth, digability, learning curve, and many others factors which may be derived from the drillhole data. These parameters often change as a function of the location in the reserve base, and may also vary with time."

Jan 1, 2016

Mill #4 processes mildly refractory ore from Carlin Trend deposits. Diagnostic analysis of plant operating data was used to generate a mathematical model containing the important parameters influencing gold recovery. The model was used to direct modifications to plant operating practice. The cyanide-dosing strategy was changed to reduce gold losses from preg-robbing and to cut reagent consumption. A finer grind was achieved without capital investment. The density in the carbon-in-leach circuit was lowered, and tighter control was exercised over the plant throughput. These changes resulted in a recovery increase of at least 2%, worth $111,000/month at $300/oz ($9.64/g) gold, and concomitant reagent cost savings of $55,000/ month.

Jan 1, 2000

By E. Watkins, S. J. Schatzel, V. Gangrade, R. Kimutis, J. Addis, C. Hollerich

The recent shale gas revolution in the United States has led to the drilling of hundreds of unconventional shale gas wells in active and future coal reserves in traditional coal-mining regions of Pennsylvania, West Virginia, and Ohio. This paper summarizes the impact of a shale gas well breach on the mine ventilation system of an operating longwall panel. This study utilizes a 1:30 scaled Longwall Instrumented Aerodynamic Model (LIAM) to simulate a single-panel longwall operation. The LIAM will be utilized to identify flow pathways and distribution patterns of gas from breached gas well scenarios in an operating longwall in the Pittsburgh Coal Seam. Sulfur hexafluoride (SF6) tracer gas is utilized to simulate a breached gas well. Preliminary findings suggest that the breached gas is diluted to regulatory levels and does not accumulate in the mine entries or in the longwall gob when the longwall panel is adequately ventilated. Overall, this study characterizes the potential interaction between shale gas wells and the mine environment in the event of a gas well breach, which provides critical information to the industry and regulatory agencies for improving safety, health, and welfare of miners.

Mar 2, 2022

By MARK J. VANARELLI

Estimating groundwater inflows in rock deep tunnels is critical to the safety of personnel constructing the tunnel and the cost of construction. This paper presents two case studies for estimating steady-state groundwater inflows into deep rock tunnels. The case studies included the Chattahoochee and Nancy Creek tunnels. In this paper, statistical methods were applied to packer test data obtained from exploratory borings during geotechnical site investigations. A semi-empirical procedure was utilized for estimating groundwater inflows into these deep rock tunnels. The Chattahoochee and Nancy Creek tunnels are deep rock tunnels which exhibit radial flow conditions. For the radial flow condition, a statistical analysis presented in this paper indicates that the semi-empirical procedure works well; however, variations in the procedure and/or an insufficient amount of testing could lead to underestimations of the inflow quantities. Packer test data plotted in histograms were observed in all cases to be log-normally distributed for the radial flow condition. Modeling using Monte Carlo simulations was observed to be an effective tool for removing irregularities in the distribution of the data and incorporating high-end permeability data to derive reasonable groundwater inflow estimates.

Jun 13, 2021

By Charles Kimbell, L. Nahai, E. Shekarchi

INTRODUCTION AND SUMMARY World mineral trade during 1960 to 1984 has shown substantial changes both in value and tonnage. Although fuel commodities dominated total mineral trade during this period, this paper will focus attention primarily on nonfuel minerals. Brazil and Australia, modest producers of iron ore in 1960, have become dominant producers and exporters, together accounting for about half of major iron ore exports in 1984, far surpassing traditional export suppliers such as Sweden. Australia has also become the largest producer and trader of bauxite and alumina, and worldwide alumina trade has increased at the expense of bauxite trade. Similarly, shipments of ferroalloys have increased more than shipments of ores such as those of chromium and manganese. Canada, retaining its first rank in world export of zinc, has become also the leading source of potash and sulfur in world trade, and South Africa has been the dominant factor in chromite, manganese and their respective ferroalloys. Developing countries' share of world copper trade has increased, with Chile maintaining first rank, but developed industrialized countries have continued to dominate production and trade of lead and zinc. Phosphate, sulfur, and potash have been the principal crude nonmetallic minerals traded worldwide. Looking to the near future, dramatic increases in export of iron ore, phosphate, potash and sulfur are not envisaged. Bauxite exports will continue to decline relative to alumina but at a slower rate than in the recent past. Zinc concentrate will continue to be exported but lead will be traded more as metal than as concentrate. For iron and steel, there will be some production shift from traditional producers to certain developing countries and recently industrializing developing countries such as Brazil, India, the Republic of Korea, and Taiwan. In the following sections dealing with specific commodities, it should be understood that information is presented only on the major forms of each commodity that move in trade, and only for a selected group of countries for each commodity or major form of each commodity. Thus, totals shown or mentioned generally represent only the totals of figures presented here and do not include estimates for minor forms of material or for countries that are not listed. However, the data provided is regarded as sufficiently complete to reflect major patterns and trends, and exclusions are there- fore not seen as affecting conclusions that may be drawn from the material provided. FUEL AND NONFUEL TRADE Values of Fuel and Nonfuel Trade The value of world export trade in major mineral commodities (ores, concentrates and scrap, crude minerals, iron and steel, nonferrous metals, nonmetallic minerals and mineral fuels) in 1983, the latest year for which comprehensive data are available, was reported by the United Nations in May 1985 to have totaled over 514 billion current U.S. dollars (Table 1). This was 79% of the historic record high of nearly $649 billion ,current dollars set in 1980, but almost 18 times the current dollar value reported for 1960. [1/] The value of these 1983 exports in constant 1960 dollars was $164 billion (Table 2), only 66% of the record 1980 high of almost $250 billion, and only about 5.7 times the 1960 dollar level.

Jan 1, 1986

By T. McCallum, C. Cooper, B. Hutzler

"In copper solvent extraction, managing the quality of the organic phase is a key parameter to ensure optimal physical and metallurgical performance in the plant. Increased throughput as a result of declining ore grades coupled with advances in plant design and practice, resulting in reduced organic losses, has pushed the limits of the status quo with respect to organic quality. Clay treatment of plant and recovered organic at the optimal dosage is critical in maintaining quality, however, achieving the optimal dosage through existing filtration capacity and practice can be difficult. Cytec has developed a process aid that increases efficiency of existing filtration equipment that has been successfully implemented at two commercial SX operations. ACORGA® CB1000 enables higher dosages of clay while allowing for more efficient use of existing filtration capacity. This study analyzes results from commercial trials and demonstrates that improved organic quality and clarity is achievable through optimization of current treatment practices. INTRODUCTION Decreasing ore grades have prompted copper solvent extraction operations to raise PLS flow rates, increasing plant throughput to maintain production1. The ability to process higher flow rates through existing mixer-settlers historically came at the expense of increased entrainments2. However, advances in mixer-settler design, practices and improvements in organic recovery processes have enabled operations to maintain, and in some cases reduce organic losses while achieving higher flow rates through existing equipment. Based on the increased demand on the SX equipment and reduced losses (or more efficient recovery) maintenance of the circuit organic quality through efficient clay treatment is now more important than ever. This paper discusses common industry practices and related issues in organic clay treatment, and presents benefits achieved in commercial operations through the use of ACORGA® CB1000 Clay Binder. IMPROVEMENTS IN DESIGN AND PLANT PRACTICE Mixer-settler design has improved since the first commercial copper SX operation in the late 1960s. Advanced designs in mixer, settler, and settler internals have contributed to reductions in entrainments. For example, improved impeller designs have been reported to decrease organic in aqueous entrainment from the ‘old designs’ of 50-200 ppm3 to as low as 4 – 10 ppm confirmed via diluent and reagent consumptions . Similarly, operations are reporting a 20-50% decrease in reagent consumption when compared to the original design criteria3. Operations have optimized settler internals to increase coalescence and have improved settler operating practices which have been shown to reduce entrainments7. Comparison of the SX world operating data from 1999 and 2007 shows reductions in organic entrainment losses with increases in flow rates."

Jan 1, 2015

By J. R. Brett

Utah Development Company (UDC) operates five large opencut coal mines in the Bowen Basin of Central Queensland, Australia. In total, over 20 million tonnes of coking coal are exported annually from the five mines. Typically, the coal seams dip at 5 percent, are 2 to 10 metres thick, and sub-crop some 20 to 40 metres below surface. In the main, the operations are single seam, but multiseam (2, 3 or 4 seams) operations do exist and will form an increasing proportion of the mining activities as depths increase. Draglines are used as the major stripping equipment, highwall depths currently ranging from 20 to 65 metres. Whilst project feasibilities were based on stripping to a 60 metre highwall, it is now proposed to continue opencut mining to depths exceeding 100 metres. This will entail large quantities of prestripping (ahead of the draglines) and overcoming problems associated with steepening seam dips, including haulage of coal from the pits.

Jan 1, 1982

"Metallurgical process development in greenfield projects must define the comminution flowsheet and establish the equipment sizes that are required to deliver the project design criteria. These are critical steps that heavily influence the financial performance of the project, requiring a detailed understanding of the ore properties of the project resources and the best practice methods to size comminution machines. This paper reviews current practices for determining the ore characteristics relevant to comminution circuit design. Particular attention is given to the design of sampling and testing programs, and the methods commonly applied to size crushers and mills for conventional size reduction applications in mineral processing. IntroductionMetallurgical process development in greenfield projects requires the selection of a comminution flow sheet and must establish the equipment sizes required to deliver the project design criteria. This necessitates a detailed understanding of the ore properties that define the project resource. For brownfield projects the same objectives may apply for plant expansions, or the project objective may be simply to define the capacity and operating cost of an existing facility for a new ore source. The process development phase in either instance will typically comprise the following key activities:• Geometallurgical classification and sampling of the ore deposit or deposits.• Determination of comminution energy requirements.• Benchmarking similar projects.• Identification of flow sheet options.• Equipment selection and sizing.This paper is concerned specifically with process development testing and will as such focus on the first two activities on the list: sampling and testing of the deposit. The discussion will focus on testwork programs to support the design of comminution circuits commonly in use in mineral processing today, specifically crusher, tumbling mill and stirred mill technologies.It is important that any testwork program is designed giving consideration to the types of flow sheets that are viable for the project, and the data that will need to be generated to support the final equipment sizing. Designing a testwork program to only provide information about one particular type of flow sheet will not allow sufficient information to be generated for a rigorous trade-off analysis of options, and may therefore preclude financial optimization of the project. Testing programs should be designed to collect sufficient data to ensure that any backtracking at a later stage to fill in missing information is minimal."

Jan 1, 2016

By Ralbern H. Murray

Typical First Year Selling Price Strip Mined Western Sub-Bituminous Coal Based [Fixed Capital (1) $600 MM Construction Loan Interest $100 Working Capital $ 30 Start-up Costs $ 30 Total Capital Requirement $760 MM Annual Costs (First Year) $M/Year Coal (2) 443,550 Operating Costs(3) 53,000 Depreciation(4) 36,500 Interest(5) 45,220 After Tax Profit(6) 34, 200 Federal Income Tax (48% Rate) 31, 570 Gross Revenue Required 245,040 (Less) By-Product Sales (18, 000) Net Revenue Required 227, 040]

Jan 1, 1975

By Mark Alan Marlkos

Blebs of solid bitumen from the Magmont West orebody of the Viburnum Trend were examined and analyzed in an attempt to relate hydrocarbon distribution and origin to ore genesis. The bitumen was calculated to be approximately 48 to 63 percent aliphatic and is considered to be a polymerized normal crude oil. Polymerization, which was probably caused by water-washing, hardened the bleb surfaces and appears to have "frozen" the blebs during primary migration from local source beds. Comparison of the bitumen to kerogen in local shaly partings strongly Indicates that the oil was derived locally. The polymerized oil blebs are considered to have been derived from a type II (marine) kerogen. Textural analyses indicate that oil migration occurred after lead-zinc mineralization and at temperatures that exceed normal ancient or present geothermal gradients. The following sequence of events is postulated for the Magmont West orebody: 1 Generation of hydrogen sulfide during diagenesis of a normal organic-rich carbonate sequence. 2 Introduction of pulses of hot, metal-rich fluids that resulted in: a Lead-zinc mineralization by the following reaction: Me++ + H2S ? MeS + 2H+ b Solution of carbonates by excess acid produced during the above reaction. c Brecciation of host rock in some cases. 3 Passages of the pulse resulted in: a Carbonate buffering of fluid system to more alkaline conditions. b Precipitation of dolomite c Slight temperature drop. 4 Eventually the high temperatures Introduced by heated brine caused oil generation and initiated primary migration. 5 Water-washing and mild biodegradation altered the hydrocarbon blebs to their present composition.

Jan 1, 2013

By Charles Dumaresq

The management of mine tailings poses a complex range of potential risks, including physical risks, such as the risk of catastrophic failure of a tailings facility and chemical risks such as the risk of long-term leaching of contaminants into the downstream environment. If these risks materialize, they can lead to a wide range of impacts on people and the environment, including human fatalities and severe impacts on downstream ecosystems, and the costs of recovery borne by industry, communities, governments, and society as a whole can be immense. Tailings facility failures in Canada (2014), Brazil (2015 and 2019), South Africa (2022), and in other locations around the world underscore how high the stakes are when mines produce and manage tailings (WISE Uranium Project 2019). Understandably, many people do not trust the mining industry to manage tailings responsibly. As an industry, it is our responsibility to manage tailings in a manner that is responsible and strives to minimize harm associated with tailings management, including effectively managing both the physical and chemical risks associated with tailings. Standards have an important role to play in responsible tailings management by setting expectations for standards of care and providing a means to measure and report on performance. In jurisdictions with strong legal requirements for tailings management, standards play a complementary role, pushing performance improvements in areas that may be difficult or impossible to address in legal requirements. In jurisdictions where legal requirements are lagging, standards may represent the de facto leading practice and may be the primary tool to help ensure responsible tailings management. Implementation of standards can help companies demonstrate that tailings are being responsibly managed and help build trust and credibility. Most importantly though, standards are important tools to help ensure that the risks associated with tailings are reduced, and that remaining risks are effectively managed. However, we must recognize that conformance with standards can have a down-side – the proverbial two-edged sword. Having standards is vital but there is a risk that implementing standards becomes a “box checking” exercise, with ongoing conformance leading to complacency. We must not allow ourselves to fall into the trap of believing that, just because we are complying with applicable standards and laws, we are therefore doing our best, and that “it can’t happen to us.” In addition, if conformance becomes the goal and the standard does not have mechanisms to drive continual improvement, then once the standard is met, there may be no incentive to improve. The point of complying with standards is not to pass the test. The point is to manage tailings responsibly, prevent catastrophic failures, and minimize harm. The point is to do better, because we must do better. To do that, we need to strive not for conformance, but for excellence in tailings management, driven by continual improvement and a quest to do better.

Feb 1, 2025

By Crystal Poon, Paul Matlashewski, John Morkeh, Kathryn Dorfschmidt, Jose Carvalho, Chad Williams

Rockfall hazards are ubiquitous in mining environments making their control critical for safe mining operations. The complex processes involved in rockfall events necessitate a probabilistic modeling approach with well-calibrated material properties. The controls designed to mitigate rockfall hazards need to be reliable, efficient, and safe to deploy to meet the constraints present at an active mine. This paper presents an innovative solution to rockfall at Rio Tinto’s Bingham Canyon Mine. The solution incorporates the site-specific calibration and creation of a predictive rockfall model with the design, field testing, implementation, and monitoring of the rockfall controls.

By D. -P. Georgescu

A native sulfur mineralization associated with pyrite and iron oxides containing 20% iron was quarried in Calimani Mountains, Oriental Carpathians. The wastes resulted from this exploitation activity, with a volume of 33 millions m3, were stored in four dumps while the wastes resulted from ore processing using flotation and the subsequent treatment were disposed of in a settlement pond. The investigations carried out in the entire mining area focused on the following two aspects: - the impact of environmental factors mainly on the hydrographic network; - the characterization all pollution sources, namely dumps, leachates and the quarry and the assessment of acidic drainage generation. The total sulfur content of the excavated ore was 3.8% while in dumps it ranged between 0.54 and 1.06%. Analysis of samples collected along the hydrographic network, draining the mining area, resulted in pH values ranging between 1.7 and 2.83 as well as high concentration of iron (4525 mg/L to 1.6 mg/L), copper (1.87 mg/L to 0.04 mg/L) and zinc (13.13 mg/L to 0.3 mg/L). Samples from the quarry, the dumps and the tailings pond were analyzed in order to deter-mine: - the maximum potential acidity (MPA); - the acid neutralization capacity (ANC); - the net acid production potential (NAPP).

Jan 1, 2005

By Mingju Liu

The coal and gas outburst accident on May 20, 2007 at Sihe Coal Mine is unique in that there was no or very little soft coal in the coal seam and that the coal strength was very high. The outburst also showed that there was a very high gas content of 20-30 m3/t in the coal seam nearby the outburst site. Based on the field test and observations, together with laboratory experiments, detailed analysis was conducted on the controlling factors of coal and gas outburst potential at Sihe Coal Mine. Stress data available from Sihe Coal Mine, northern China, and other parts of the world, were also taken into account to facilitate the analysis. The results shows that the stress level was not abnormal compared to other coal fields in China prone to outbursts, and that gas contained in the coal seam was the main factor that triggered the outburst. All these factors were essentially controlled by the tectonic evolution features in Qinshui Coal Basin, to the Southeast of which Sihe coal field is located. Based on the analysis, assessment of coal seam outburst potential was carried out by measurements of coal seam gas contents, observation, and detection of soft coal layers in the coal seam. The results show that outbursts are limited to only a small part of the whole coal seam and that the eastern part of coal field is not prone to outbursts.

Jan 1, 2009

By R. E. J. Putman

Rising demand, artificial market conditions, increased overseas competition, and a fluctuating international situation have brought ever increasing pressures to bear on the nonferrous metals industries, and particularly in the United States, Although capacity is being expanded by the construction of new plants and the development of new ore deposits, increasing attention is being focused on the possibilities of improving the performance of the existing installations and of getting the most out of the new equipment now installed. At first sight the task appears formidable. Based on raw materials which are nonhomogeneous, and possessing characteristics which are hard to quantify, even the processes by which the values in the ores are concentrated and extracted are in many cases not fully understood. The necessary analytical equipment and transducers demanded by these industries have also been slow in development and their earlier absence has hampered the application of modern control technology, This is reflected in plants which have been designed for ease of manual rather than automatic control, and in which the application of control techniques at first sight appears economically prohibitive. However, in any industry progress often comes only in small steps, It may be that by the wise choice of limited objectives and perhaps only partial solutions, substantial improvements in plant performance can be implemented now, and with only a modest investment. If modern control equipment is chosen of the type which can be reprogrammed, advantage can be taken later of more sophisticated solutions as the technology of the industry advances. This task of improving plant performance can and must be commenced even though our knowledge is incomplete. The experience of a related mineral consuming industry, with similar problems in the past, can be encouraging.

Jan 1, 1967

By G. R. Addie

While the cost of transporting raw phosphate matrix from a pit to a processing plant via slurry pipelines is more efficient than it could be by rail cars, conventional trucks or belt conveyors, it still amounts to many millions of dollars, and in many areas there still exists much room for improvement. By taking advantage of pipeline test data on different slurries, it is possible to reduce costs by optimizing pipeline diameters, operating velocities and slurry concentrations. Better wearing, more efficient pump designs are now available which, if applied correctly, can lead to significant savings. The authors discuss what benefits are possible in relation to the electrical operating and wear maintenance costs and go into some of the factors associated with taking advantage of these benefits, identifying what they see as being practically possible.

Jan 1, 1998

By Baojie Zhang

The main goal of this study was not only to investigate the effectiveness of the FGX Dry Separator for removing pure rock from run-of-mine coal producing a better feed stock for conventional coal preparation plants but also to optimize the FGX Dry Separator performance for producing a salable clean coal product without using the conventional wet coal preparation processes. A Model FGX-1 Dry Separator with feed throughput capacity of 10 tph was extensively tested at the Illinois Coal Development Park using two coal samples having distinctly different cleaning characteristics. Statistically designed experimental programs were conducted to indentify critical process variables and optimize FGX Dry Separator performance by systematic adjustments of critical process variable parameters. The coal cleaning performance of the FGX Dry Separator was evaluated for the particle size range of 63.5 x 4.76 mm in most cases, although FGX Dry Separator feed consisted of nominal -63.5 mm run-of-mine coals. The best cleaning performance obtained from the FGX Dry Separator is described by specific gravity of separation (SG50) and probable error (Ep) values of 1.98 and 0.17, respectively. The SG50 and Ep values for individual size fractions were as follow: 1.90 and 0.12 for the +50.8 mm size fraction, 1.95 and 0.18 for the 50.8 x 25.4 mm size fraction, 2.01 and 0.19 for the 25.4 x 12.7 mm size fraction, and 2.03 and 0.23 for the 12.7 x 4.76 mm size fraction. These process efficiency measures produced a clean coal with ash content of 13.38% from a feed coal with ash content of 34.45%. Ash content of tailings and middlings streams were 85.09% and 39.57%, respectively. Total sulfur contents of corresponding streams were 3.87%, 4.68%, 6.87%, and 4.62%. For a relatively easy to clean Illinois No 6 seam coal (Cleaning Index: 0.72), only about 0.42% of the clean coal (i.e., 1.6 float fraction) present in the feed was lost to the tailings stream. For a relatively difficult to clean coal (Cleaning Index: 0.53), about 0.98% of the clean coal present in the feed was lost to the tailings stream.

Jan 1, 2012

By Rodney R. Krause

In attempting to tell the general public about the coal industry's land reclamation efforts, we have often said, "We're not doing things by the book, because we're still writing it." Like any good catchphrase, the statement is not only striking but true. It is particularly true in the mountains of Appalachia, where the problems of mining; and of reclamation are made more intense by the nature of the terrain. Mining and reclaiming the land "by the book' --which is to say by the methods of contour mining traditionally used in hill country--hasn't worked too well. So a lot of conscientious coal operators and associations are trying new methods--new ways of mining, new machines for seeding and planting, and new species to seed. Not all their experience can be transplanted to other areas, and of course I don't believe that Appalachia is the only place where new methods are being developed. Nevertheless, there's enough action in Appalachia to make a detailed examination rewarding, so let's focus on the hills to see what's new.

Jan 1, 1970

By C. D. Litton, I. E. Perera

This report presents the results of experiments to evaluate different types of mine fire sensors in an underground mine environment using a commercially available atmospheric monitoring system. To determine how well carbon monoxide (CO) and smoke sensors respond for purposes of fire detection, experiments were conducted using test fires of different mine combustibles and for both flaming and nonflaming combustion. The experiments were designed to assess the response of fire sensors to different contaminants and different contaminant levels produced from the test fires. The experiments were performed in the Safety Research Coal Mine at the U.S. National Institute for Occupational Safety and Health’s Bruceton Research Facility in the presence of an average ventilating air velocity of 1.6 m/s (315 fpm). Five fire sensor stations were located downstream of the test fire at fixed locations, with each sensor station consisting of four sensors: a CO fire sensor and three different smoke sensors, of which two were evaluated by the Mine Safety and Health Administration (MSHA) for intrinsic safety and the third was used extensively in underground mines overseas but not evaluated by MSHA for intrinsic safety. All four sensors were mounted near the center of the entry and in the upper onethird of the entry height. A UL-listed combination ionization and photoelectric smoke sensor was mounted near the roof at the first sensor station and its responses were compared against the responses of the four CO and smoke fire sensors. Sensor response data, contaminant travel times, and the impact of fire on the existing ventilation flow are discussed as they apply to earlywarning fire detection. Of significance in the analysis is the need for performance standards for mine fire sensors in order to provide for consistent and timely early warning of developing fires.

Jan 1, 2014

By George E. Valadão, Iván A. Reyes, Mizraim U. Flores, Armando C. Araujo, Rubén H. Olcay

Dewatering tailings to higher grades than paste produces a stable deposit that typically does not require retention dams and is called a “dry stack.” A proposal of different dewatering techniques applied in the fine tailings produced after final desliming phase, obtained from the treating of phosphatic ores, is the main objective of this work. The dewatering techniques evaluated were column thickener, deep cone classifier, and hyperbaric filtration. Calcite and dolomite were the main mineral contained in the phosphate tailings and these have a very fine granulometry; the tailings presented different behaviours related to the dewatering technique applied. The test column thickener and deep cone classifier with the best operational parameters found to obtain a maximum percentage of solids in mass were ~ 71% and ~ 67%, with values of yield stress ~ 200 Pa and ~ 100 Pa, respectively. In the hyperbaric filtration, a cake with ~ 10% moisture was obtained. This indicates that the transportation conditions are not the same. The overflow turbidity levels obtained from column thickener and deep cone classifier test did not exceed the value 100 NTU, whilst for the filtrate of the hyperbaric filter obtained values ~ 800 NTU. It was possible to preliminary estimate the recovery direct of water, considering each dewatering technique for final disposal of the tailings. The best dewatering techniques obtained were in the following order for the disposal in phosphate fine tailings dams; the hyperbaric filter showed an excellent dewatering capacity with productions rates around 160 kg h− 1 m− 2 for moisture cake of 10%, followed by the column thickener and deep cone classifier with paste ~ 71% of solids (W/W) and high-density slurry ~ 67% of solids (W/W), respectively.

Dec 23, 2023