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ABB Industrial Systems is one of the largest electrical engineering companies in the world. ABB develops, manufactures and markets electric drives. The company has more than 100 years experience in the application of medium- and high-voltage AC machines. And ABB's continuous research and development program ensures that its machines use the latest technologies and materials. Each motor is custom designed to meet specific applications. The HXR high-efficiency motors (100 to 1,900 kW or 134 to 2,250 hp at 50 Hz) are efficient and have low noise levels. Typical applications are pumps, fans, blowers, compressors and pulverizers. The enclosed units are constructed with external cooling ribs and fans. And the motors are equipped with solid, longlife stators and rigid rotor construction. The patented rotor construction provides for low vibration levels. ABB's large synchronous motors (1 to 50 MW or 1,340 to 70,000 hp up to 900 rpm) are used in the mining industry for crushing, grinding hoisting and conveying systems. These motors are designed to customer's specifications, including existing foundations. They can be equipped with fixed or adjustable speed control.

Jan 1, 1998

By Elif Emil-Kaya

Samarium (Sm), as one of the rare earth elements (REEs), has gained significant attention in the production of samarium- cobalt (SmCo) magnets due to their high corrosion and oxidation resistance, as well as their high-temperature stability. SmCo magnets find applications in various industries, including but not limited to national defense, aerospace, military and medical equipment. Sm and Co have been classified as critical metals due to their economic importance and supply risk. Recovering Sm from SmCo magnets is an effective method to ensure a stable supply. The present study investigates an integrated hydrometallurgical treatment and combustion process for the preparation of rare earth oxide (Sm2O3 ) powders from SmCo. Initially, SmCo powders are exposed to nitric acid, and the resulting slurry is selectively oxidized at 250 °C to obtain Sm(NO3)3 , Co2O3 and Fe2O3 . Subsequently, the selectively oxidized powders are leached with water to extract Sm. Sm2O3 powders are produced from the obtained leaching solution using an energy- and time-efficient solution combustion process. Finally, the optimal conditions for the production of Sm2O3 are identified, and the produced powder is characterized through X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM) analysis.

Nov 1, 2024

By Jr. Raleigh

In a cooperative agreement between the U.S. Bureau of Mines and the U.S. Department of Energy, laboratory column-flotation tests were conducted to evaluate fluorosurfactants as selective fine coal flotation collectors. A Middle Kittaning seam coal responded to flotation with both anionic and nonionic fluorosurfactants. These fluorosurfactants were no more selective than MIBC alone. However, for increasing coal yields, nonionic fluorosurfactant systems did not increase total sulfur and ash contents as sharply as MIBC systems. Flotation selectivity also improved slightly when a combined anionic fluorosurfactant-MIBC system was used in acidic pulps (pH < 3.6). While the fluorosurfactants examined will not likely have direct application in current coal flotation practice, other fluorosurfactant systems could eventually prove beneficial for floating fine coals.

Jan 1, 1990

By K. A. Natarajan, M. R. Sabari Prakasan

"Biodegradation of sodium isopropyl xanthate using two types of bacterial strains, Paenibacillus polymyxa and Pseudomonas putida, is demonstrated. At concentrations higher than 50 mg/L, the presence of xanthate in the growth medium resulted in bacterial toxicity, retarding growth kinetics. Adaptation through serial subculturing in the presence of higher xanthate concentrations resulted in the development of xanthate-tolerant bacterial strains. Stress proteins secreted by bacterial cells grown in the presence of xanthate were isolated. Bacterial cells could utilize xanthate as a growth substrate, degrading xanthate species in the process. Acidic metabolic products generated by bacterial metabolism promoted efficient xanthate decomposition. Probable mechanisms for the biodegradation of isopropyl xanthate are illustrated.IntroductionDifferent types of alkyl xanthates (ethyl, isopropyl, amyl, etc.) have been used as flotation collectors in the concentration of sulfidic ores for several decades. Large quantities of waste water and xanthate-containing effluents are generated by ore flotation processes, posing considerable environmental challenges. Billions of cubic meters of such process waste waters are produced annually across the world, most of which are discharged to the environment, often without any treatment. Leakages and accidental release of xanthate reagents from manufacturing plants and during transportation and storage can also contaminate the environment. Residual concentrations of xanthate reagents are encountered in waste effluent, which are found to be toxic to aquatic life and unfit for human consumption (Harris, 1984; Okibe and Johnson, 2002). Further, direct recycling of such waste waters for plant operations can compromise water quality standards required for process operations. The presence of residual xanthate in recycled waters from flotation plants deleteriously influences flotation processes. Xanthate can be easily decomposed at low pH values; however, CS2, which is more toxic, will be produced by the acidification of neutral and mildly alkaline xanthate-containing solutions. Physico-chemical methods such as flocculation, chemical oxidation and decomposition and physical adsorption used to remove residual collector reagents from mill process waters are often expensive and not environment-friendly (Oliveira and Rubio, 2009; Cheng et al., 2012; Molina et al., 2013,)."

Jan 1, 2015

By T. Gupta, T. Ghosh

"In recent years, the demand for Rare Earth Elements (REE) have grown rapidly due to increasing demand and global supply shortage. The supply deficit of these critical elements has encouraged the search for new sources of REEs, possibly Coal and Coal byproducts. Coals from certain parts of the world can be rich in REEs, and can approach a total concentration of 1000 ppm. Two Alaskan coal samples were investigated for the effect of size and density on the concentration of REEs on three selected size fractions. Flotation tests were conducted for finer fractions. Additionally Bottom ash and Fly Ash samples from a power plant have been examined for REE concentration. The results show that the upgrade potential for REEs on ash basis from whole coal basis ranges from 2:1 to 4:1 for Wishbone Hill and Healy coal samples respectively. Flotation of the finer fraction for both coal samples, conducted under similar conditions, reveal higher concentration of REE’s in the tailings. Both coal samples have a comparatively higher LREE content than HREE. Trends of REE content of the power plant products on ash basis revealed that Fly Ash has a slightly higher concentration of both LREE and HREE than Bottom Ash. Keywords: Rare Earth Elements, Coal, Coal Ash INTRODUCTION Rare Earth Elements (REEs) and their compounds are vital components in industrial, automotive, petrochemical, defense and medical applications. Dysprosium in combination with other elements is used in laser materials and nuclear control applications. Neodymium is present in magnets that are used in green power generation such as the manufacture of wind turbines and also in hybrid cars. Europium, Terbium and Yttrium are used for devices that have visual displays such as computer screens and laptops [1, 2]. REEs pose fewer environmental problems of disposal and recycling than conventional heavy metal counterparts [1]. Rare-earth metals are key ingredients for radar systems, avionics, modern national defense and satellites [2-8]. In the last 25 years China has been mining, processing and refining Rare Earth elements at affordable prices thus gaining a virtual monopoly in the market. The many fold rise of the prices of REE elements over the last few years and frequent disruptions in supply has forced various nations to invest in indigenous extraction of REEs by increasing production from previously productive sites and to expand the production from new alternate sources including coal and coal byproducts [9]. Coal and Coal beds have been found to be significantly enriched with certain critical metals and can be a potential source for both Light Rare Earth Elements (LREE) and Heavy Rare Earth Elements (HREE) [10]. Moreover, coals with high REE concentrations have been discovered in Pavlovka and Rakovka coal deposits in Russia, Appalachian deposits in USA, Sichuan Basin deposits in China and others across the globe [10-13]. A recent study from China looked at how different trace elements (including numerous REEs) partition in various size fractions of Antaibao coal from China. The finding indicates that the REEs, phosphorous, and thorium all have their high concentrations in the particle sizes 0.5 to 3 mm, and 6 to 25 mm. REEs are also often present in the form of phosphates such as monazite in coal [13, 14]. The objective of the study is to identify the concentration of REEs in Alaskan coals and to investigate the effect of density and size in the distribution of REEs in coal and coal byproducts."

Jan 1, 2016

By Howard W. Earnest

The Rio Blanco Oil Shale Company completed a modified in situ oil shale retorting demonstration at its Tract C-a Lease in the Piceance Creek Basin of northwestern Colorado during the spring of 1982. This demonstration was the first MIS project with shafts rather than adits for access to the mining operation, and it involved several potential hazards which required that particular attention be paid to mine ventilation. Methane was first encountered during shaft sinking and ultimately resulted in the mine being classified gassy by MSHA. Secondly, we encountered hydrogen sulfide in association with the ground water, and this proved to be a more persistent problem than did the methane. Thirdly, in order to burn the underground retorts, it was necessary to provide for potential leakage of retort gases and to obtain a modification to the MSHA standard which forbids fires under- ground. This modification had a significant effect on the ultimate ventilation procedures at Tract C-a. An extensive under- ground air monitoring program was included in the ventilation system.

Jan 1, 1983

By Dafydd Chandler, Milissa Hirst, Charles Hurst, Gary Snyder, Leszek Glodkowski

The Delaware County Regional Water Quality Control Authority (DELCORA) will be adding tunnel infrastructure to its wastewater conveyance system. This program involves the construction of a conveyance/storage tunnel and related facilities. The proposed 12- foot to 14-foot (±) finished diameter, TBM mined deep rock tunnel spans over 8.5 miles and lies approximately 80 ft-120 ft below the surface. The system is connected to the surface by at least five vertical online shafts and one offline shaft with associated 800ft long adit. This paper provides project details including data on the geologic conditions in which the tunnel will be constructed.

Dec 1, 2022

By E. R. Phelps

It is very seldom that a completely new project is initiated. Most projects consist of a new and different combination of proven techniques or a combination of proven and new techniques. The theme of my discussion today falls in the second category. Proven methods of water transportation and proven methods of bulk material handling were combined with some new techniques which resulted in a new market for the coal industry and a cheaper fuel supply for the power industry. In this respect I refer to the water transportation of coal from the West Kentucky coal fields to coal burning power plants on the west coast of Florida. Peabody Coal Company, Florida Power Company, Gulf Coast Transit, and Mid-South Towing combined their individual requirements and "know how&apos; to make this project possible. I feel the results speak for themselves since it proves that coal can be mined in the West Kentucky coal fields, transported some 1,200 miles by river barge and some 450 miles by ocean going barges, be delivered to power plants on the west coast of Florida and still meet the competitive prices of gas and residual oil. The unique parts of this project concerns the storage and trans loading facilities for coal from river equipment to ocean equipment near New Orleans; the return haul of phosphate and it&apos;s trans loading from ocean to river equipment at the same facility and the use of large ocean going barges. In detail it works as follows: Coal is mined in West Kentucky and loaded into 1,500 ton river barges on the Green River. It is then transported some 100 miles to the mouth of the Green on the Ohio River, then 200 miles down the Ohio to it&apos;s convergence with the Mississippi, and then 900 miles down the Mississippi to the trans loading facility some 40 miles South of New Orleans. There it is transferred from the 1,500 ton river barges to 18,000 ton ocean going barges and hauled some 450 miles across the Gulf of Mexico to the Gannon Station of Tampa Electric at Tampa entailing a total haul of approximately 1,650 miles.

Jan 1, 1966

By B. G. Hicks

The Manapouri Power Project is located in New Zealand&apos;s South Island Fiordland. The project is being constructed for the New Zealand Ministry of Works. Construction began in 1963 and is scheduled&apos; for completion in 1969. The project will divert water from the natural, glacially carved Lake Manapouri, at Elevation 580, through vertical- penstocks into an underground powerhouse 364 feet long, 127 feet high, and 59 feet wide excavated about 700 feet below ground surface and about 560 feet below the present lake level. The possible ultimate power installation will produce 700 megawatts from turbines located in the underground machine hall. The turbine flow will discharge through the 6-mile, 30-foot diameter tailrace tunnel into a fiord arm of the Tasman Sea. The rocks in the project area are primarily Paleozoic Fiordland Complex gneiss, schist, amphibolite, and marble intruded by granitic rocks and pegmatite. Shear zones have been encountered in the tunnels and machine hall. These produce water and occasionally require steel support. The machine hall arch was stabilized entirely by rock bolt reinforcement. Rock mechanics instrumentation has been used throughout the project both for pre-construction design calculations and to monitor tunnel rock loads and movements of the machine hall roof and walls. About 28 miles of the 100-mile transmission line will be constructed across glacially oversteepened slopes and debris or swamp filled valleys between the power plant and the eastern edge of the mountainous area. Steep glacially carved rock slopes and locally unstable glacial till complicated construction of the transmission line access roads.

Jan 1, 1968

By E. C. Roper

Landusky Mining, Inc. and Zortman Mining, Inc. are two registered Montana Corporations wholly owned by Pegasus Gold, Ltd. of Vancouver, B.C. The Zortman and Landusky Mines are located in the Little Rockies District of central Montana. The Zortman-Landusky mines produced 2,100 kg gold in 1982. A total of 3,250,000 t of ore per year are mined during the period March 1, to September 15, at an average grade of 1.04 gm/t (0.03 oz/t) gold and 13.4 gm/t (0.385 oz/t) silver at a cutoff grade of 0.35 grams of gold/ton (0.01 oz of Au/t) of ore. The stripping ratio during 1983 is anticipated to be 0.75/1 waste to ore. Combined average plant capacity of the two Merrill-Crowe plants is 9,840 lpm (2,600 gpm). The combined heap spray capacity of the two plants approaches 18,900 lpm (5,000 gpm). The mine employs approximately 200 people, about half of these work for the mining companies and the other half for the mining contractor, N. A. Degerstrom of Spokane, Washington. Net profit in 1982 for Zortman and Landusky Mining, Inc. approximated $4,900,000 at an average gold price of $11.40/gm.

Jan 1, 1983

By III Feeley

Coal is the nation&apos;s most abundant fossil energy resource and serves as the primary fuel for the U.S. electric-power industry. However, its continued and expanded use is often challenged by the nature and amount of its associated impurities, such as mineral matter, sulfur, and trace elements. The moderate- to high-sulfur content of many U.S. coals is of particular concern today as potentially more stringent regulations requiring further reductions in sulfur dioxide emissions are being considered. The most prevalent method currently employed to control SO2 emissions from coal-burning facilities is post-combustion flue-gas desulfurization. However, physical coal cleaning (a.k.a. beneficiation, preparation) methods can also be effective in removing sulfur and ash impurities from coal prior to combustion. In a typical physical cleaning operation, raw coal is crushed to about 50-mm (2-inch) topsize, and then screened into coarse, intermediate, and fine size fractions. Crushing liberates some of the ash-forming minerals, including the portion of inorganic sulfur (pyritic) not chemically bound to the coal matrix. The percentage of impurities liberated generally increases as the coal particle size is reduced. Coarse- and intermediate-sized coal particles are typically subjected to specific gravity-based cleaning methods, while fine-sized (less than 0.5-mm) coal particles are beneficiated using froth flotation, a technique based on surface property differences. Greater cleaning potential exists at finer sizes because of increased liberation of impurities, but this potential is not fully realized because of inefficiencies associated with fine particle separation using state-of-the-art coal cleaning technologies.

Jan 1, 1990

By A. Martikainen, H. Dougherty

"At the Kemi Mine, a recent expansion into the Surmaoja orebody required an increase in ventilation capacity. A new ventilation shaft was built with two main fans. The installation is near the entrance gate and only 1.7 kilometres from the nearest permanent dwelling. The main fans were first taken into use as exhaust fans in October 2014. Shortly after the fan installation, comments concerning fan noise were received from the neighbours. The first noise measurements were taken at the main fan installation site by Outokumpu personnel in March 2015. Due to higher than expected recorded values, during late June, 2015, a two-week environmental noise study was planned by the engineers and executed by a consultant specialized in noise measurement. The measurement results were analysed and compared to the requirements of the environmental permit and Outokumpu’s factory standards. While the measured values at the nearest dwelling were within the environmental permit limits, high noise values were recorded at the fan station. A second two-week study will be performed after construction of the main-fan heating station has been completed. Actions taken will depend on the outcome. INTRODUCTION The Kemi Mine is a part of the Outokumpu chain of integrated ferrochrome and stainless steel manufacturing in the Kemi-Tornio region in Finland. The mine itself is a large underground operation with a production capacity of 2.7 million tons of ore per annum. It is also the European Union’s only chrome mine, and at present (2015) the mine extracts 2.4 million tons of chrome ore per year. Safety, cost-effectiveness, and environmental friendliness are hallmarks of the Kemi Mine. Environmental impact produced by the operation of the mine is limited due to the insolubility of the oxide chromium ore, the gravity-based and chemical-free enriching process as well as the closed circulation system of the process water which serves both the whole mine and the enrichment process (Outokumpu, 2015). Importance of the environmental impact of the Kemi Mine is amplified by its closeness to the cities of Kemi and Keminmaa with the nearest habitants living less than 2 km away from the mine site. To show the cooperation with residents the Kemi mine organizes special “neighbour days” for the habitants of the areas closest to the mine. Also, information letters are sent to the neighbours, when changes that may affect the neighbours are being planned and executed."

Jan 1, 2016

By David Morrison

"The history of the mining industry is littered with in-pit crushing and conveying (IPCC), which should not be confused with the International Protocol for Carbon Capture, projects that failed. The failure is not the technical one of “did it achieve the desired tonnage rate for a longish test period” but, rather, the far more important one of “did it provide return on the investment in the manner that was promised?” While quite a few can claim the former, very few system installations can claim the latter.The reasons for the many failures are numerous, but they are all characterized by a combination of an element of engineering optimism in any, or all of the production rates, the productivity, or the operating and maintenance costs and in predicting the continuity of operating conditions. In these days of big data, propagating such a situation is rapidly becoming unforgivable.In this article, the three most common scenarios put to the corporate board for approval, and the logic as to why they were selected, are examined (with the irony included intentionally).• Fully mobile crusher, fed by a shovel and conveyed out of the pit to a waste dump / process plant.• Semimobile crusher (much more expensive than a fixed crushing station but which apparently allows trucks to short haul inside the pit and improve productivity), which moves when the face moves.• Relocatable crusher (more expensive than a fixed crushing station but which gets relocated at great expense after all the fixed infrastructure impeding relocation is demolished) fed by trucks that don’t leave the pit mostly.This paper will also consider the truth about their operational performance and associate costs."

Dec 1, 2016

By Tony Treasure, Ian Ewart

The EMEW® cell has been developed to overcome a number of inherent limitations in conventional electrowinning technology, particularly the high cost and restricted process windows characteristic of conventional hardware. The EMEW technology has been widely demonstrated to achieve high performance for various metals under chemical conditions well outside the limits required for efficient operation of conventional cells. In particular application of the EMEW cell for recovery of silver offers significant operating and capital cost advantages over conventional Merrill Crowe technology used for cyanide based solutions. The cell also offers process advantages for direct silver recovery from nitric acid solutions. The performance of the EMEW® cell on silver cyanide solutions, producing high grade silver metal in a single step, is accomplished by providing a physical mechanism which presents metal ions to the cathode on a highly efficient and continuous basis. The simplicity of design and operation of the EMEW cell offers the following advantages for silver recovery from cyanide or nitrate based solutions: • High grade product in a single step. • Selective for silver over other metals in the electrolyte. • Wide operating concentration range (100,000 - 5ppm). • Ability of the cell to operated in a variety of acid or alkaline electrolytes. (Cyanide, Nitrate). • Simple liquor reticulation. • No pretreatment required - Clarification, deaeration or zinc dust. • High cmTent density and current efficiency compared to conventional electrowinning cell. • Modular design allows for flexible operation and production rate. • Pilot plant results using full scale cell result in accurate scale up design. • Easy/fast installation - cell banks are delivered pre configured with piping and wiring. • Enclosed cell minimizes corrosive vapor and liquid losses in the circuit.

Jan 1, 2000

By H. -J. Langhoff

"The paper describes not a result, but a starting point to implement sustainable development to a region characterized by a typical down river landscape, agriculture, and extractive industry. The NaturFreizeitNiederrhein GmbH (NFN) is a private company with associates from administrative bodies, the local mining companies and multiple representatives of environmental protection groups (local and national), tourism organizations, cultural societies and also aquatic sport and fishing clubs. Center of the concept is the "NFN Lake District." The development concept aims to provide the agricultural industry with alternative means of income, while protecting wildlife and the ecological balance as well as preserving the social und cultural system and enhance the safety against flooding from the river Rhine. The mining industry contributes their coordination of obligation concerning reclamation and recultivation of the already existing individual projects. While designing the landscape components and establishing the infrastructure for the different tasks, the production of gravel and sand is yield as a by product. The result is a long term perspective for region and industry."

Jan 1, 2005

By S. K. Kawatra, H. J. Haselhuhn

"Fine-grained hematite ore can be concentrated by the process of selective flocculation and dispersion, which relies on proper reagent selection and control of water chemistry. While many previous studies have been performed analyzing the effects of different reagents on this process in a laboratory environment, this paper focuses on investigating the water chemistry within the process in a pilot-scale continuous deslime thickener.The pH, sodium concentration, calcium concentration and magnesium concentration were varied to determine their effects on the iron concentrate grade and recovery, and the phosphorus concentrate grade and rejection in the pilotscale selective deslime thickener. The ideal pH for the iron grade and recovery of the process using a starch selective flocculant was found to be 10.5. Phosphorus rejection, however, was increased at lower pH values. Minimization of sodium concentration was shown to improve iron grade, iron recovery and phosphorus rejection. Calcium acted as a nonselective flocculant showing higher iron recovery, lower iron grade and lower phosphorus rejection with increasing concentration. Conclusions could not be drawn from the experiments that varied magnesium concentration.The zeta potential of the solid-liquid interface of particles in each sample taken was also analyzed to show relationships between zeta potential and process performance. In all cases, a maximization of the magnitude of zeta potential correlated with increased iron grade and recovery. This supports the hypothesis that a higher level of dispersion enhances the selective flocculation and separation process.IntroductionThe United States produced 53.2 million metric tons out of the 3,000 million metric tons of concentrated iron ore produced worldwide in 2012 (Tuck, 2013). With this in mind, there has been a large increase in iron ore processing research (Bolen, 2014; Carlson and Kawatra, 2008, 2013; Halt and Kawatra, 2014; Halt et al., 2014; Haselhuhn et al., 2012a,b, 2013a,b; Liu et al., 2014; Manouchehri, 2014; Sandvik and Larsen, 2014; Semberg et al., 2014). Of the 53.2 million metric tons produced, roughly 8 million metric tons of hematite (Fe2O3) concentrate were produced using a process known as selective flocculation and dispersion (Cliffs Natural Resources, 2011). This process is the only economically viable method for concentrating low grade (< 40% Fe) fine grain (< 25µm liberation size) hematite ores. It is scarcely used due to difficulty in controlling the surface chemistry of the ore and high reagent costs (Department of Energy, 2001; Haselhuhn et al., 2013a). The process is highly dependent upon both reagent selection and precise control of the water chemistry during separation. This study shows the dependence of the process performance of a pilot-scale deslime thickener on the water chemistry in the feed slurry."

Jan 1, 2015

By James H. Boettcher

In the second quarter of 1979, ASL Inc. inquired whether Crocker National Bank ("CNB") would provide $4 million in term loan financing to help ASL acquire the outstanding shares of the S&S Coal Company in West Virginia. ASL had, prior to approaching CNB, sought financing with the assistance of a financial advisor from a number of commercial banks without success. A summary of the initial terms requested by ASL is shown in Table I compared with the actual terms the transaction closed with. It is not difficult to note that the two sets of terms differ significantly. This is often the case when financing requests based on the expectations and vision of a mine developer are juxtaposed with more pragmatic requirements of a commercial bank. The "art" and fun of structuring financing plans for mining ventures (highly leveraged acquisitions or grass roots) comes in working with mine developers to arrive at a final financial structure that meets their objectives and constraints as well as those of the bank or other financial institution providing much of the financing. This article briefly describes the process we went through with ASL beginning with the terms they requested initially and ending with the ones on which the transaction was finally closed.

Jan 1, 1981

By R. Larry Grayson, Joel R. Warneke

The mining industry has searched for a message that will resonate with the public while focusing on the industry’s positive contributions to society. So far, environmental groups remain unconvinced and the public is still largely uninformed. In the authors’ opinion, a number of recent events and experiences have converged to help shape a more effective public communication on mining’s important role. This article presents a perspective on coal’s role in sustaining society by anchoring the message in a transparent way, including a material flow analysis, that links coal’s impacts across a range of social and environmental aspects. Past and continuing image problems In her 1994 paper, Nancy Bingham, with Caterpillar, outlined what the public thought about mining. Based on extensive interviews, the following results were found: • The public believed mining harms the environment. • The public believed mining harms people in nearby communities. • The public believed mining exploits workers. • The public believed mining has little personal benefit to the individual.

Jan 1, 2006

By Y. Pan, P. Tukkaraja, R. BHARGAVA, V.V.S. VYTLA, S.J. SRIDHARAN

Panel caving is an underground bulk mining method that uses gravitational force to mine massive, steeply dipping and deep-seated ore deposits at lower operating cost. To control dust and gas emissions entering the production level during the extraction of ore from the draw points in a panel cave, relatively negative pressure is created in the cave by installing an exhaust fan in the exhaust drift located on top of the cave. As caving is a dynamic process, designing an effective ventilation system is challenging; therefore, estimating the airflow resistance offered by the broken rock inside the cave is critical. This study investigates the effect of changes in the bulk porosity of the broken rock on the cave airflow resistance using the computational fluid dynamics (CFD) approach. The results show an inverse relationship between the cave airflow resistance and the bulk cave porosity. The pressure-quantity characteristic curves presented in this paper provide valuable information for sizing and operating an exhaust fan used for a mature panel cave ventilation.

Nov 1, 2022

By Robert L. Zook

Coal refuse slurry impoundments are dams constructed of coarse coal refuse to impound fine refuse (slurry) and water (25-30% solids). Both products are waste from coal preparation plants. A number of these structures in West Virginia, Pennsylvania and Kentucky were investigated to determine embankment stability. During the investigation a variety of embankment designs were encountered. The investigation determined the soil and geological characteristics of the embankments and the sites. This was accomplished by a test drilling and monitor installation (observation wells and piezometers) program, geologic study, and large scale mapping which allowed sub-surface profiles of the embankments to be constructed. The laboratory testing program concentrated on textural classification of the coal refuse, permeability and determining strength parameters to be utilized in the stability analyses. For the stability analyses, the Modified Fellinius Slip Circle, Simplified Bishop Slip Circle and Analysis for Translational Failure -were utilized. In all stability analyses hydrostatic pressure and earthquake were considered. This investigation indicated that 62% of the embankments analyzed are in a stable condition. The coal seam mined, the type of roof rock, and the gradation of the refuse influence the degree of compaction obtainable and the permeability of refuse. The shear strength of coal refuse appears to be controlled by its composition, moisture content, degree of compaction, amount and grain size of fines present. This investigation demonstrated these em¬bankments should not be treated as pure state-of-the-art dams; consideration must be given to the particular properties of coal refuse and the total refuse disposal system. Refuse dim slurry impoundments generally lack the site se- lection phase that is standard practice with siting most other types of dams.

Jan 1, 1974