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By C. A. Rowland

The use of the Bond Work Index to size industrial grinding equipment is well known. Its use to measure grinding efficiency was presented by C.A. Rowland, Jr. at an AIME meeting in 1976. However, due to a bureaucratic error, the paper was never submitted for publication. This metric has nevertheless been adopted by industry as a widely used standard. The purpose of this paper is to re-present and update the application of this tool as a standard for measuring grinding circuit efficiency. Definition ?standard, n. something established for use as a rule or basis of comparison in measuring or judging capacity, content, extent, value, quality, etc.; as standards of weight and measure? (Webster, 1958).

Jan 1, 2008

By John M. Arnold

Several years ago it became apparent to some of our people that; there was developing a very definite need for largee coal reserves in the West to satisfy- the need for fuel for the furnaces of electric generating plants with the rapid development of, the West, of both population and industry, it was impossible for hydro-electrics plants to keep up with the ever increasing demand for electricity. In 1960, Mr. E. R. Phelps, then associated with the engineering department of Peabody Coal Company, began a search for and development of coal deposits in the very remote northeast section of Arizona near the village of Kayenta. Travel to this section of the country was not easy even at this late date, and it was an eight hour drive from Farmington, New Mexico to Kayenta, Arizona, a distance of some 130 miles. The trip was over roads that even' a-horse and wagon had trouble negotiating and a four wheel drive vehicle was about the only type of transportation that could satisfactorily traverse these roads, as testify many badly beaten sedans and coupes that tried it. Since that time a very excellent road has been constructed from Shiprock; New Mexico to Cameron, Arizona where it junctions with another excellent road that runs north to Page, Arizona and the Lake. Powell area and south to Flagstaff, Arizona on highway 66. Kayenta is a small village nestled at the foot of the Black Mesa near its northeast extremities. The coal deposits of interest were on the surface of the mesa. This location presented another problem, as the only trail to the top of the mesa was intended for walking, horseback, or a brave soul In a horse and wagon. Once again the four wheel drive vehicle was about the only answer. To reach the coal deposits you must climb the mesa, which is vertical ascent of some 1,500 feet, and then proceed southward into the bowl of the mesa with an ensuing descent of some 1,000 feet, finally coming to an elevation of 6,500 feet, at which elevation the coal outcrops become apparent.

Jan 1, 1969

By S. Managi, M. C. Williams, N. H. Behling

Particle processing is a key to using solid particles in fuel cell applications. Selectivity with regard to reactivity, impurities, etc. is important feature and the treatment of particle surfaces could greatly impact the performance of direct carbon fuel cells. Solid fuel particles will become increasingly important in the future. Present energy conversion systems for solid fuels are too inefficient. New energy conversion systems for solid fuels with higher energy conversion efficiencies are possible. Fuel cell technology is a key-technology in these new conversion systems. The direct carbon fuel cell (DCFC) operates on carbon particles obtained from a variety of solid fuel feedstocks. The DCFC is the only fuel cell designed to directly oxidize carbon particles in a special anode chamber. The particles are generally graphite structure with high purity. The electrolyte used is the high temperature solid oxide, molten carbonate or hydroxide electrolyte. Since a pure stream of CO2 is produced the stream can easily be sequestered and disposed. Pure carbon dioxide produced as a by-product would also have a market in many industries. A well-defined technology roadmap identifying key research and development (R&D) issues is necessary to provide a framework for the development of these systems and to prevent entrenchment in inherently inefficient technologies. This review paper describes the direct carbon fuel cell and its system, how it works, the developmental status, the characteristics of the carbon particles needed, and the research and development issues for the technology. INTRODUCTION The DCFC has been under development for many years. It was researched as early as 18961), but an intense research and development is necessary to realize its potential. William W Jacques, a US electrical engineer and chemist, described a DCFC in 1896 in US Patent 555511 for a “Method of converting potential energy of carbon into electrical energy”. Jacques used coke electrodes in a molten NaOH electrolyte. Molten carbonate fuel cell (MCFC), solid oxide (SOFC) or hydroxide electrolyte (AFC) technologies can be used as the basis for the DCFC technology. A schematic of the direct carbon fuel cell in the MCFC mode is shown in Figure 1. The molten carbonate fuel cell operates at approximately 650°C (1200°F). The high operating temperature is needed to achievesufficient conductivity of the carbonate electrolyte, yet allow the use of low-cost metal cell components. A benefit associated with this high temperature is that noble metal catalysts are not required for the cell electrochemical oxidation and reduction processes. For the hydrogen reaction the half-cell electrochemical reactions are

Jan 1, 2019

By P. J. Ryan

Phelps Dodge’s Candelaria copper-gold mine is located 20 km (12miles) south of Copiapó in northern Chile’s Atacama province (Region III) (Fig. 1). The Candelaria Mine is about 800 km (500miles) north of Santiago and 75 km (47 miles) east of the Pacific Ocean. Its elevation is 600 m (1,970 ft) above sea level. The Copiapó River Valley is 6 km (4 miles) northeast of the mine site. It is the only major source of water in this arid region. The average rainfall is 14mm/a (0.5 in./year). During 1995, the mine produced 521.4 kt (574,800 st) of copper concentrate containing 150 kt (165,000 st) of salable copper and 3 t (98,800 oz) of gold. The 1995 unit cash cost was less than 50 cents/lb of copper. This makes Candelaria one the world’s lowest cost copper producers.

Jan 1, 1996

By Andrew Chegwidden, Tara Wilk

Shaft 18B-1 is the second shaft to be constructed as a part of contract C547A along the New York City water supply system Tunnel No. 3. More complex than Shaft 17B-1, this site has an additional 30 m (100 ft) of overburden for a total excavation depth of approximately 78 m (256 ft) through water-bearing overburden soil and 145 m (475 feet) of gneiss bedrock to connect to the underlying Water Tunnel No. 3. round freeing was specied as the method to provide temporary earth support and ground water control for the overburden material. An extensive supplemental geotechnical investigation (SGI) and frozen soil testing program was performed to develop the design of a temporary ground freezing system, consisting of over 7,315 m (24,000 ft or 4.5 miles) of drilling for the installation of 95 freeze pipes. At the start of shaft excavation, the upper sandy silts strata was found to have an unprecedented low thermal conductivity, leaving the frozen soil face approximately 0.6 to 1 m (2–3 ft) behind the cutline. The ground freezing earth support needed to be augmented with ring beams and liner plates to support this soil face and allow for the excavation to proceed and be completed safely.

Jun 23, 2024

By H. Mischo, R. Ellmies

Uranium has been mined in Namibia since the 1970s. The worldwide increasing need for energy in the early 2000s has led to the development and opening of a second uranium mine in 2007 and has triggered an increased interest in uranium exploration, often referred to as “the Namibian Uranium Rush.” In all, four mining licenses have been granted by the Namibian Government, which currently has two mines in operation, a third undertaking trial mining and the fourth in project finance negotiations. In addition, highly intensive prospecting activities at additional deposits are at an advanced stage. The finalization of the strategic environmental impact assessment (SEA) on uranium mining in 2010, the first of its kind and scale in the world, has enabled the Namibian government to assess this uranium rush and its tremendous legal, socioeconomic and environmental impacts and to prepare for the different future scenarios conceivable when this article was written in 2011, including both a skyrocketing and a complete breakdown of demand scenario. The Fukushima disaster and plans of the Namibian government to significantly increase royalties and company taxes in 2011 have threatened the market situation, forcing investors to reevaluate Namibian uranium mining projects. However, with the tax and royalty increase initiative since withdrawn, most projects are back on track at this point in time.

Jan 1, 2012

By C. Patrick

Longwall face-to-face transfers can cost over $100 per minute in lost production potential and $100,000 for personnel and supplies. Such high cost makes extensive planning and control of the transfer process a critical necessity for the economic feasibility of longwall operations. This paper reports operations research techniques used for the analysis and modeling of longwall face-to-face transfers. Transfer data has been collected from companies who operate over 30% of the total U.S. longwall faces. Comprehensive sequence networks of existing longwall transfers were developed; simulation models of transfers under varying conditions were generated; and, the economics of general transfers and time-cost tradeoffs in the transfer procedure were investigated.

Jan 1, 1993

By R. Frim, S. D. Ukeles

The present U.S. production of bromine is from inland brines located in Arkansas and Michigan. The most concentrated domestic brines (up to 5,000 ppm bromide) are situated in Arkansas. Less concentrated brines (about 2,500 ppm bromide) are located in Michigan. The amount of bromine sold or used in the United States came from three companies operating in Arkansas and Michigan. Arkansas, with its six plants, was the leading U.S. state in bromine production. Bromine being the leading mineral commodity valuewise produced in the state. The Michigan bromine production was a byproduct of magnesium compounds production.

Jan 1, 2006

By Morgan M. Sears, Gamal Rashed, Michael M. Murphy, Brent Slaker

In this study, a parametric study was conducted using FLAC3D numerical models to examine the impact of oblique loading, generated from seam dip, on the strength and the failure propagation pattern of a stone pillar using two simplified geometry types. In type 1, the sidewalls of the pillars were assumed to be perpendicular to the roof and the floor, while in type 2, the sidewalls of pillars were assumed to be vertical. The complex pillar geometry in dipping mines was frequently modeled using these two geometries. To capture a complete picture of the effect of seam dip on pillar stability, the modeled width-to-height (W/H) ratio of the pillars, in situ stress field, and pillars roof/floor interfaces were systematically varied to account for the potential distribution of values for these parameters across the underground stone mines in USA. Results from the numerical modeling indicate that dipping pillars have reduced strength compared with horizontal pillars. Also, an asymmetric failure propagation pattern could be obtained depending on an interaction between the W/H ratio, seam dip, in situ stresses, and pillar geometry.

Feb 5, 2021

By J. Hart, P. W. Conrad, S. Rosenthal, R. A. Hogan

The Mining Engineering Department at Montana Technological University (Montana Tech) has a new Mine Safety and Health Administration (MSHA) approved program for Part 46 and Part 48 mine health and safety training. The training program will utilize the facilities and faculty from Montana Tech’s Mining Engineering and Safety, Health, and Industrial Hygiene departments to provide superior mine health and safety training to the mining industry. The faculty of each department includes professionals with experience in safety training and the mining industry. The training program incorporates adult learning techniques and extensive hands-on activities in all training modules. The instruction will exceed MSHA requirements. The resources available on Montana Tech’s campus will be utilized to strengthen the training program providing the mining industry with a world class mine health and safety training program.

Feb 1, 2023

By Jiawang Hao, Qinglong Zhang, Liang Han, Chuhan Wang, Shenfang Chen, Lan Qiao

The surface collapse and surrounding rock failure caused by goaf instability are the mining disasters that cannot be ignored. It is of great value to evaluate the stability of goaf accurately and treat it economically for the mine safety and the maintenance of ecological environment. However, in previous studies based on numerical simulation methods, the spatial complexity and the irregularity of actual goaf were not considered. Therefore, based on the internal space data of goaf obtained by high-precision laser detector, the goaf stability was comprehensively analyzed through Plaxis software and two-stage fuzzy judgment theory in this study. To effectively improve the goaf stability, the optimal backfill parameters for the goaf treatment were obtained by a series of mechanical tests. The research results provide some good references for the stability evaluation and the treatment of underground goaf.

Sep 26, 2023

By Maryam Motamed, Jeremy Stone, Leigh Anne Zhang

Controlling and predicting ground movements are essential to the design of shoring systems. The Courthouse Commons tunnel in San Diego, California, included a 56-foot-deep temporary shaft as a launching point for tunneling using the Sequential Excavation Method (SEM). The rectangular shaft was unique in that it was surcharged on one wall by an 11-story building and employed a hybrid support of excavation design. An array of geotechnical instrumentation was used to monitor lateral and vertical movements at the ground surface. This paper compares the measured ground movement with the predicted ground movement from various excavation stages

Dec 1, 2022

By Yucheng Li, De Huang, Yonghong Liu

Mine frictional resistance is one of the essential parameters of mine ventilation systems, and it is of considerable significance for the prevention and control of mine risks and accident hazards. Frictional resistance requires a lot of resources and time and has errors. To reduce the errors of frictional resistance, a regression model of frictional resistance is proposed based on the correlation analysis of the affecting factors. Through the comparative test analysis of seven regression methods, it is found that the classification and regression tree method for solving the proposed regression model has better performance than other methods. The least square error criterion is used to calculate and rank the importance of the factors affecting frictional resistance. The results show that the cross-sectional area of the tunnel, the support method, and the presence or absence of devices or pedestrian ladders have the most considerable influence on the prediction accuracy of frictional resistance. The support methods and cross-sectional areas are essential input variables. Through the combination test analysis of the influencing factors, the results show that the regression model does not have predictive ability when the number of input variables is less than 3 and the best predictive performance cannot be obtained using all the influencing factors. The best prediction model of resistance is to combine the shape of the tunnel, the support method, the presence or absence of devices or pedestrian ladders, and the cross-sectional area. The method proposed in this paper does not require a lot of resources and time investment, and the frictional resistance error is small. At the same time, it solves the problem of resistance prediction with incomplete data of influencing factors and provides a compelling new method for obtaining frictional resistance parameters.

Jan 28, 2022

By J. H. van Laar, C. S. L. Schutte, M. Le Roux

Highly energy-intensive systems prone to wastage are significant causes of unnecessary energy losses in industry. Deep-level mine chilled water reticulation systems fall within this category of inefficient energy-intensive systems. Some techniques (measured baselining, zero-waste baselining, leak detection, and control valves) exist to identify and reduce wastage in mine water reticulation systems. However, these techniques have not been compared, which begs the question of which is more accurate. A need, therefore, exists to compare these methods to determine the effectiveness of each. This study investigates each method and applies them to a case study mine, providing a platform for comparison. These methods identified wastage ranging between 2 and 20 l/s (3–30% of water consumption). The comparative effectiveness of the methods from best to worst was found to be zero-waste baselining, leak detection, control valves, then measure baselining. This study proposes an application procedure combining the considered methods to identify and eliminate wastage on deep-level mine systems more efficiently.

Jan 31, 2024

By Matthew S. Sanchez, Richard J. Lee, Matthew D. Zock, Drew R. Van Orden

"Current Environmental Protection Agency (EPA) risk models and asbestos fiber counting techniques for monitoring airborne exposures treat all fibers as being equivalent and ignore the effect of dimension on toxicity. While this may have been appropriate when modern analytical methods were not available, the measurement world is now fully capable of making the appropriate distinctions. The importance of width as a determinant of carcinogenicity has been recognized for nearly 30 years within the published literature. Stanton,1 in a landmark study of a suite of fibrous materials, found that durable mineral fibers with widths less than 0.25 mm and lengths longer than 8 mm were causally associated with the induction of tumors. Pott,2 in a later study, postulated a fiber toxicity model that agreed reasonably well with the Stanton findings, but extended the concept to include varying toxicity as a function of length and width. Wylie et al.3 reanalyzed samples used by Davis et al.4 and found that tumor generation was strongly and inversely correlated with fiber width. Crump5 testified increasing fiber length was correlated with disease occurrence. Lippman6 reviewed a number of studies and suggested that mesothelioma was closely associated with long, thin fibers. Berman et al.7 published a risk model, which found that disease was correlated almost exclusively with fibers longer than 40 mm and width less than 0.25 mm. Recently, Loomis et al.8 reanalyzed textile mill samples and found that aspect ratios greater than 40:1 were highly correlated with disease. Incorporation of width into risk models has been limited by the availability of data from operating asbestos plants and, in particular, the observation of an asbestos plant for which there is no observable mesothelioma. There have been only limited studies published on the dimensions of asbestos fibers, with a few serving as the primary references in other literature.9_13 A rare opportunity to collect detailed concentration and dimensional data of airborne crocidolite from an operating asbestos-cement plant using modern analytical procedures arose, providing a chance to supplement the existing literature on airborne fiber dimensions. The asbestos-cement plant is located in the eastern end of Cochabamba, Bolivia along Highway 4. Cochabamba is a relatively large city located in the Andes Mountains, approximately 250 km southeast of the capital La Paz. The city sits in a valley that runs east-west with mountains to the north and south. The crocidolite used in the products made at this facility is mined in central Bolivia, approximately 75 km northwest of Santa Cruz. The crocidolite is a fibrous magnesioriebeckite 14 (blue asbestos). Crocidolite fibers from Bolivia were the subject of prior reports suggesting the fibers are generally longer and thicker than crocidolite from Australia or South Africa.9 At the cement plant, the run-of-mine crocidolite was first pulverized using a hammer mill and then sieved on vibratory sieves to produce fibers of limited size ranges for use in the cement. The sieved crocidolite is mixed with other components, including recycled cement product, to produce a slurry that is vacuum filtered into sheet form. The sheets are then manually molded into a corrugated shape, air dried, and sawed (using circular saws) to accepted dimensions. The sawed sheets are cured in soaking pits for 28 days before being shipped to the consumer. Prior to shipping, the sheets are finished by a light hand sanding followed (at customer request) by applying one or more coats of paint. A detailed description of the cement plant and the industrial hygiene results can be found in Van Orden et al.15"

Jan 1, 2012

By S. S. M. Chan

The design of most underground support systems has largely been based upon empirical rules. This design method has proven to be satisfactory in most cases as witnessed by the number of successfully completed works. However, the adequacy of this approach to the developing technology of ground support systems associated with deep excavation has not been substantiated. In cases where the material has definite time-dependent behavior parameters, rules of past experience become extremely vague and conservative. The Spokane Mining Research Center is currently engaged in extensive research to develop rational design methods for underground structures which will account for the many interacting factors such as in-situ properties of the rock mass, excavation methods, proposed types of support system, construction sequence, and environmental variables. The information presented in this paper pertains to only a segment of the research program,

Jan 1, 1971

By Jupneek Singh, Zachary A. Kiehl, Leila Safazadeh, Gareth Kennedy, Eleonora Widzyk-Capehart, Jeremy W. Ward

Mine workers are continuously exposed to a host of nonfatal stressors and potentially fatal hazards: noise exposure, excessive vibration, poor air quality, toxicant exposure, ignition of combustible gases, equipment-related accidents, and thermal heat stress. Wearable or portable sensors and contextual analytics provide a platform to unobtrusively collect and fuse multimodal health and safety data in real time to compute both acute safety and longitudinal health insights. This paper presents preliminary trial results, conducted by Simtars, VigiLife, Inc., and Queensland Mines Rescue Service, of the application of wearable sensors to monitor heat stress and other vital biometrics for mines rescue personnel.

Feb 1, 2024

By M. T. Ityokumbul

The use of yield index, the product of the yield and gangue rejection, for the optimization of separation processes is presented. The characteristics of the yield index are contrasted with separation efficiency calculations and applied to laboratory froth flotation and washability data. Data from continuous froth flotation tests conducted to "optimize" froth flotation using process optimization software were also evaluated with the yield index procedure.

Jan 1, 1997

By James A. Jessop

The Bureau of Mines is investigating the use of geophysical methods to determine rock mass characteristics, particularly rock quality, lithology, and fracture parameters that are important for determining the feasibility of in situ leaching operations. As part of this research, two Bureau-developed crosshole geophysical systems are described that can be used for site investigation and rock mass characterization. Results are given for performance tests at field sites in Arizona and Texas and for correlations between the crosshole seismic data with fracture frequency, rock quality, and lithologic variation. Recommendations are made for using elastic waveform propagation characteristics and dynamic elastic properties for improving rock mass characterization in the geomechanical assessment of in situ leaching deposits.

Jan 1, 1990

By Ayokunle Adewale Akinlalu, Sunday Bayode, Sherif Olumide Sanusi, Joshua Oluwagbenga Adeboye

Gold occurrences have been reported in Alagbede, southwestern Nigeria, but a mineral potential map (MPM) to guide academics and investors in the area is still needed. As a result, geophysical methods (aeromagnetics and aero-radiometry) have been used to assess the potential for gold minerals in the area. Several enhancement filters, such as reduction to the equator, upward continuation, analytical signal, second vertical derivative, and power spectrum analysis, were applied to the aeromagnetic data to understand the subsurface geology better. The enhancement filters applied to airborne radiometry data are K/eTh, ternary color composite, F parameter, and deviation from the ideal K values (Kd). Geophysical data analysis was used for structural mapping and geological reconstruction, while aero-radiometric data was used for hydrothermal alteration mapping. The primary trend observed in the area’s magnetically inferred structural framework map is NE-SW, while a few are in the NW–SE and E-W trends. These observed trends show that the study area suffered at least three deformation episodes. Geological evidence of gold mineralization, such as favorable lithology, geological structure, and hydrothermal alterations, has been fused to produce a reliable MPM of the area. The geographical location of the existing mineral sites in the investigated area agrees with the geological structures and the MPM produced there. Thus, the systematic approach adopted in this study can be extended to other supracrustal belts of a typical Precambrian basement complex worldwide to ensure the reliability of orogenic gold mapping and resource management.

May 9, 2023