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By S. K. Kawatra, R. A. Seitz

There is considerable variation in the types of coal flotation circuits in use in various parts of the world. For example, Russian plants frequently use scavenger flotation, while this is almost unheard of in the United States. The numerous circuit designs are intended to address specific problems in coal flotation, or to take advantage of the peculiarities of certain coal deposits. As a result, it can be difficult to decide which circuit is best for a given application. For this paper, coal flotation circuits were collected worldwide from many operating plants. These circuits include varying degrees of conditioning, and complexity ranging from simple rougher flotation to multi-stage split- stream processing. The design goals of each circuit are described, and the advantages and disadvantages of each are discussed. Extensive sampling campaigns were carried out in two plants with the most common types of coal flotation circuit (simple rougher, and rougher with deslimed feed). The performance of each plant was evaluated, and the benefits of more sophisticated processing in each case are described.

Jan 1, 1993

By R. R. Oder, R. J. Gray

We report measurements of the effects of rank, type, and grade of coal on grinding energy and grinding media consumption in a Pitt Mill. The rank of coal has a greater effect on grinding energy than does coal type. The effect of coal grade on grinding energy depends upon the relative grindability of the mineral matter and of the hydrocarbon components of the coal. The mineral matter is primarily responsible for abrasive media wear in a Pitt Mill. The widely recognized HGI test for coal breakage may yield misleading results, particularly for multiple-banded bright and dull coal where the screening procedure used in sample preparation favors the testing of the hardest coal fraction. The work reported here indicates that the Pitt Mill, which grinds the whole coal in a single stage and which yields easily interpreted results, is an excellent candidate for testing coal pulverization characteristics including energy requirements and equipment wear. The measurements of the effects of coal characteristics on grinding energy and on media consumption have been used to estimate the cost of fine grinding in a Pitt Mill. The results, based on a conceptual level evaluation of grinding at the rate of 1 TPH, show that there are trade-offs possible between the cost of energy and cost of media consumption which involve choice of grinding media size. The use of fine-size grinding media to lower grinding energy and to increase throughput can be deceptive because the total cost of grinding must consider both energy and media consumption.

Jan 1, 1992

By Nikhil Dhawan, Veeranjaneyulu Rayapudi, Singh Rahulkumar Sunil

The ever-increasing demand for steel and the subsequent depletion of high-grade ores requires the massive utilization of low-grade iron ores. In the present study, an iron ore slime sample containing 56.1% Fe was investigated using physical beneficiation, carbothermal reduction, and a microwave-assisted process; however, physical beneficiation and microwave exposure were found to be inefficient as they yielded lower iron recovery. Using coconut shell as an alternative reductant was found to be promising and does not lead to the formation of higher iron oxides, such as fayalite and wustite phases. The microwave-assisted carbothermal reduction was found at par with conventional reduction, saving time and heating. The optimum magnetic concentrate obtained in both carbothermal reduction routes (microwave and muffle furnace: Fe grade, Fe recovery, and yield of 64.3, 97, and 84%, and 67, 99, and 83%, respectively) are suitable for alternative iron-making or blast furnace units.

By Donald D. Born

Mine No. 95 is located in Harrison County about 5 miles west of Shinnston, WV, with coal properties covering the northwest corner of Harrison County and the southwest corner of Marion County and with adequate Pittsburgh seam reserves to support the mine for many years. The mine was opened in 1967 and was planned, projected and operated as a room and pillar mine. It is located on a spur branch of the Baltimore and Ohio Railroad, has rail loading facilities and shipped by rail during its development stage. In 1972 it was converted to a mine mouth power station supplier and now transports coal by conveyor belt directly to the Harrison Power Station of Allegheny Power System. In 1971 the first longwall unit was installed in a selected area of the mine and immediately an orderly system of planning was developed to overcome the restrictions associated with longwall mining. The first was the development of the technique necessary for the plugging of abandoned oil and gas wells that existed in the area. With the assistance of the Morgan- town Energy Research Center of the Bureau of Mines, this restriction was overcome and thus opened a great potential for longwall mining in northern West Virginia. Other restrictions that had to be considered for longwall planning were dwellings and other improvements, snap top zones, water courses, and adequate bleeder systems, and the handling and treatment of mine drainage. In 1975 the second longwall unit was installed and soon therefore became a total longwall mine.

Jan 1, 1986

By K. W. Harris, K. A. Perry

Underground coal mines beneath Black Mountain in the Harlan County district of the Central Appalachian coalfields have an extensive history of bump events, which yields an elevated probability for significant injury or fatality to underground miners. According to Mark (2009), Harlan County has had the greatest concentration of deep-cover retreat mining in the United States. Combined with the extensive multiple seam mining history, room-and-pillar coal bumps have had a disproportionate impact on coal operations in this region. The Harlan seam, one of the principal, economically recoverable coalbeds exploited beneath Black Mountain, has a significant burst history that extends into modern times. A numerical investigation using the LaModel software of 17 bumps that occurred at the same mine in the Harlan seam was conducted and used to create a calibration methodology which serves as the quantitative basis for current and future numerical efforts in an adjacent mine exploiting the same reserve. In addition to this numerical study, a qualitative assessment of the geologic factors that are believed to contribute to the bump potential was completed. Combined with stability prediction using the numerical basis, these geologic factors will be used for recognition of high bump potential areas with the goal of reducing the potential for future bumps, helping to ensure the highest level of safety and productivity for underground personnel.

Jan 1, 2016

By George E. Peacock

Campbell Red Lake Mine is situated at Balmertown, in the Red Lake District of Northwestern Ontario, Canada. This area is some 120 miles north of the Trans Canada Highway and is some 160 miles Northeast of Winnipeg, Manitoba. The majority of our 300 employees live in Balmertown, which is a community of some 1,200 people, situated adjacent to the mine proper. The mine is serviced by a single shaft 4,300 feet deep. There are 27 levels at 150 ft. intervals. Stoping is being carried out down to the 20th level with only preliminary development having been done on the bottom 6 levels. The majority of our mill feed of 825 tons per calendar day comes from above the 10th level. Gold occurs as specks and streaks in bluish-grey to white quartz carbonate veins. It is extremely fine grained and most is invisible to the unaided eye. In addition to Gold the veins carry varying amounts of sulphides such as, Arsenopyrite, Stibnite, Pyrite, Pyrrhotite and Sphalerite. A minor amount of silver occurs as an impurity in the gold. Arsenopyrite is a marker for the gold ore at Campbell. The average grade of the mill feed is 0.7 oz. of gold per ton. The ore is dumped into an underground ore pass that feeds to a jaw crusher on the 20th level that reduces the rock to a maximum size of 4". This material is hoisted by skips to an ore bin in the head frame.

Jan 1, 1975

By H. Beecher (Original by) Charmbury

Water is a most remarkable substance, essential for life of all kinds. As well as needing water to survive, man has always used it for agriculture, transportation, recreation, and many other things. When our country was young and inhabited by few people, the streams, rivers, and lakes were able to provide all the clean water needed by man and take away all the wastes created. However, with our growing population and an ever-increasing demand for goods and services, the public, industry, and government at all levels have become acutely aware of the need to manage the nation's water resources more efficiently. Abundant energy from many sources has helped this nation to become the greatest industrial nation in the world. Coal has contributed a major portion of this energy, generating electricity, running railroads, and maintaining national security during wartime. The result has been the highest standard of living in the world and a time of widespread economic prosperity. The use of water in coal mining is somewhat different from its use in most industries. With the exception of water used in cleaning plants, for underground dust control, and for fire protection, most of the water en- countered in coal mining operations serves no useful purpose. In other words, it is an undesirable element and must be removed, otherwise it will interfere with operations, cause potential water quality problems, and may even stop operations by flooding. In the past, removing water from working areas of most mines was usually a fairly simple matter. Pumps with piping were installed at sumps or low spots in the mine and the water was pumped to the surface or to drainage control facilities constructed for the operation. Ditches were often used to collect and drain the water by gravity to the outside or to main sumps for pump discharge. In either case, the water was allowed to flow into the nearest stream or river. The concept of "water is water' was generally accepted without too much concern for what was in the water since low-cost products and services, rather than clean water, were the public demand.

Jan 1, 1981

By Nolan B. Aughenbaugh

Zoning and environmental restrictions on land usage now make open- pit quarrying more and more difficult, especially near urban areas. One option for quarry operators is to go underground for mineral production. While underground-mining costs are higher than those for open-cut work, there are several compensating advantages. In many cases it is possible to produce the same material underground without affecting land values, and the surface is preserved for industrial, residential, or agricultural purposes. Proper planning can yield underground sites which have great potential value for industrial plants, warehouses, or other business uses. It is essential to plan underground mineral extraction using a three-dimensional modular-room architectural concept to fully exploit secondary space utilization. Prior to the start of underground mining an operator must make a careful geological engineering study to deter- mine the suitability of the deposit and must prepare a plan for safe and economical mining for the purpose of converting to secondary usage.

Jan 1, 1974

By Arthur J. Borst, Joseph P. Gildner

In a recent National survey, Seattle topped the list for having the worst daily traffic congestion. To address this problem, Sound Transit is planning to build 40km (24 miles) of light rail, including ten kilometers (six miles) of twin tunnels with four subway stations 40 m (130 ft.) to 65 m (210 ft.) deep. The overall schedule is very aggressive and Sound Transit is preparing four separate heavy civil construction contracts for simultaneous underground construction. Three of these contracts are being considered for design-build. Final design will start in March2000 and all underground construction must be completed by the end of 2005.

Jan 1, 1999

By Robert W. Lawson

INTRODUCTION Prior to 1705, underground mining was limited to mineral deposits located above or a very small distance below the water table. The development of the steamdriven mining pump was motivated by the need to extract minerals from deposits considerably lower than the water table. Today, the majority of mine pumps are driven by electric motors, although some small utility pumps are driven by compressed air. Of the numerous types of pumps that might be applied to mine service, the two types used most frequently underground are the centrifugal and plunger pumps. Each of these types has its proper application. In most instances, plunger pumps are best for handling low water volumes against high heads, while centrifugal pumps effectively handle either low or high water volumes against low heads or high water volumes against high heads. This chapter describes pumps applied to underground mine service, where the mine service consists of mine drainage (removing mine water as it accumulates), mine dewatering (removing water from a flooded mine), and pumping for special applications such as hydraulic mining and hydraulic hoisting. CENTRIFUGAL AND PLUNGER PUMPS Modern mine pumps are classified as either centrifugal (kinetic) or plunger (positive-displacement) pumps. The following paragraphs describe each of these classifications. Centrifugal Pumps Centrifugal pumps may be grouped into various types, depending upon their various features: Number of Stages: In a single-stage pump, the total head is developed by one impeller, while a multi¬stage pump utilizes two or more impellers acting in one casing to develop the total head. Fig. I shows a cutaway view of a single-stage horizontal split-case double -section centrifugal pump. Fig. 2 shows a cutaway view of a six-stage medium-pressure split-case diffuser-type centrifugal pump. Type of Casing: A volute pump has a casing in the form of a spiral or volute. A circular-casing pump has a casing of constant cross section concentric with the impeller. A diffuser pump is equipped with a diffuser that converts velocity head to pressure head. Shaft Position: A horizontal pump normally has the shaft in a horizontal position, while a vertical pump normally has the shaft in a vertical position. Fig. 3 illustrates a vertical turbine-type slurry pump. Suction: A single-suction pump equips the first stage with a single-suction impeller, with fluid entering the impeller on only one side. A double-suction pump equips

Jan 1, 1982

By P. C. Kapur

The hierarchical relationship between three broad kinds of grinding models for a spatially homogeneous, linear, time-invariant batch grinding system are first established. Limiting and asymptotic arguments for arriving at approximate but simpler models are employed in all three cases. These parsimonious models -provide alternate and, in some respects, more incisive and convenient tools for the analyses of grinding processes and simulation of comminution circuits. In the discrete-size, discrete- time class of models, a reduced mill matrix is derived, which is seemingly adequate for those grinding circuits whose identification otherwise is difficult because of limitations on the quantity of data and its quality. In discrete-size, continuous-time types of models, parameter lumping has been employed for obtaining a G-H solution which is quite accurate and exceptionally useful for graphical display of data, model verification, and parameter estimation and simulation. In continuous-size, continuous-time models, a similarity transformation is used for solving the integrodifferential equation of grinding. This solution provides a unified framework for a number of apparently diverse empirical grinding phenomena such as self-preserving behavior of ground particle size distributions and energy laws.

Jan 1, 1987

By Qing-Wang Hao

In this paper, the authors attempt to develop engineering based approaches for estimating safety factors against pillar and floor failures and predicting likelihood of subsidence events over abandoned coal mines in Illinois. There are two critical problems involved in the analysis: determination of geotechnical properties, and consideration of time effect. The authors attempt to solve the problems by generating hypotheses, which are used to modify existing engineering models for estimating pillar and floor safety factors. The modified models are validated using data from two well established databases of subsidence events over active and abandoned mines in Illinois. The data analysis suggests that most of the trough type subsidence events in Illinois were caused by floor failures rather than pillar failures. The subsidence incubation period seems to be directly related to initial floor safety factors at the time of mining. This correlation can be used to predict the likelihood of subsidence and to assess subsidence risks within both spatial and temporal contexts where detailed mine maps are available.

Jan 1, 1986

By K. Biswas, S. S. Peng

The stability of pillars in old mined-out districts is greatly dependent on the weathering action caused by moisture penetration into the pillar structure. Field observations in old mining districts indicated that this weathering action becomes critical in terms of the stability of the pillar if the coal seam contains parting or binder (layers of claystone or mudstone). The weathering action caused by moisture penetration over a long period of time degrades both parting and coal. However, it has been observed that the structural deterioration is more severe in parting. Moisture-penetration rates in parting and coal are different. The extent of the weathered zone in various layers of the pillar is primarily time dependent. This paper investigates, both in the laboratory and in the field, the effects of weathering action on coal and parting. In the laboratory, slake durability indices and uniaxial compressive strength tests for dry and saturated specimens are compared for coal. In the field, the in situ strength profiles for coal and parting layers are obtained, and the effect of time (in terms of the pillar age) on the strength profiles is studied An attempt was also made to establish formulae for time-dependent strengths of coal and parting.

Jan 1, 2000

By A. Bruynesteyn

I would like to talk to you today about microbiological leaching or, the solubilization of metal values due to the action of Thiobacillus ferrooxidans. Bacterial attack of sulfide minerals has been going on for centuries but only recently was it discovered that the acid and iron often found in coal mine drainage is produced by bacterial action on the iron sulfides in the coals. Not until 1950 was it proven that bacteria were playing a role in the dump leaching of sulfide ores. B. C. Research became involved in microbiological leaching in 1955 while examining mine drainage from the copper-zinc mine at Britannia Beach, north of Vancouver. Since 1955, B.C. Research has maintained a continuous re¬search program on microbiological leaching which, due to its applied nature, was put under industrial sponsorship in 1962. Most of the information pro¬vided in my talk today has been gathered under this sponsored research program and I would like to express our appreciation to the many sponsors who have made our work possible.

Jan 1, 1970

By C. Cigna, M. Patrucco, D. Savoca, E. Lovera

The paper deals with the activity program and the preliminary results of a research work commissioned by IReR Research Centre and Regione Lombardia to the Department of Land, Environment and Geotechnologies of Politecnico di Torino. The aim is to define measurement, analysis and control criteria for the emission of chemical and physical pollutants from non-metal mining industries, with particular reference to noise and airborne particulates. Such emissions are related to health risks and annoyance problems, both for the working crews and the neighbouring population, and so, in order to get an effective sustainability of the industry, suitable reduction methods and assessment tools are required. A simple technique for the evaluation and forecasting of both the emission levels and deriving impact has been tested at different mining and quarrying sites, considering their differences in terms of layout and exploitation method, the latter ascribed to a series of main typologies as present in Lombardia region.

Jan 1, 2005

By Charles E. Glass

As partial implementation of the Surface Mining Control and Reclamation Act of 1977, the Office of Surface Mining (OSM), Department of Interior, has requested each state to inventory hazardous abandoned mining areas within their boundaries. Primary interest is in such areas .as unstable waste-banks, subsidence and slumping, contamination of water supplies, and preservation of overall aesthetic qualities through reclamation. In addition to the concern expressed for abandoned mining areas, the legislation requires a complete inspection of operating mines quarterly and a partial inspection monthly. In Arizona copper has been mined for over 100 years and coal and uranium mining promises to expand in future years. The OSM requirement for a waste inventory and frequent monitoring of Arizona's large, widely spaced mines places a severe demand on limited personnel and operating budgets. Remote sensing by satellite provides an attractive and effective approach to aid the inventory and monitoring requirements of the OSM legislation.

Jan 1, 1979

By W. G. Pariseau, S. C. Schmelter

The destabilizing effect of water pressure on rock-mass stability is examined quantitatively by the finite element method. A coupled code that accounts for the simultaneous effects of rock-mass deformation and transient fluid flow is used for this purpose. The traditional soil-mechanics assumption of an incompressible fluid is shown to be untenable for the analysis of porous, fractured rock slopes. A Mandel-Cryer effect, whish is a transitory but elevated and potentially destabilizing water pressure following a cut, was not observed.

Jan 1, 1999

By Gregory E. Korbin

The effectiveness of pre-reinforcement as an immediate stabilization measure as well as its contribution to the permanent stabilization of a tunnel were studied through the use of physical (Figure 1) and numerical models (1). Physical models were designed for the investigation of two pre-reinforcement systems: first, reinforcing far ahead of the main excavation (Figure 2); second, spiling reinforcement ahead of the face (Figure 3). In both cases, the use of reinforcement was responsible for permanently stabilizing an otherwise unstable opening. Data from the physical models were used to calibrate a numerical model from which additional information on long term behavior, methods to account for the capacity of a pre-reinforcement system, and the mechanisms involved were ascertained. These studies indicated that pre-reinforcement can stabilize a rock mass effectively as it reduces deformations and thereby deterioration due to strain softening, provides rock mass confinement leading to increased available strength, and maintains rock arch continuity allowing for increased tangential stress in the immediate vicinity of the opening. Field studies verified the capacity of spiling reinforcement to restrain initial deformations.

Jan 1, 1976

By David H. Carrillo

HYL has developed a sticking tendency test which accurately predicts behavior of iron oxide feedstocks in the HYL III process. Test results together with pilot plant experimentation and commercial scale demonstrations permit the conclusion that lump ores will not agglomerate at 960°C (1233 K) in an HYL III Plant. Pellets may also be processed without agglomeration at 960°C (1233K) with the addition of no more than 5 percent lump ore. Using the HYL III process, the ironmaker can exploit feedstock market conditions without sacrificing plant productivity or energy efficiency.

Jan 1, 1981

By Stanley C. Suboleski, C. B. Manula

INTRODUCTION In any mining operation all possible steps should be taken to increase efficiency. One area for improvement is mine planning and design, particularly in the area of equipment selection for room-and-pillar systems. Be- cause of the availability of a wide variety of face machines, a fair degree of selectivity can be exercised in the choice of equipment for a particular job. However, this choice must be made on the basis of quantitative facts and forecasts related to the mining application. The purpose of this section is to develop and analyze the details of the mining process. Some specific areas studied include the relationship of system design to productivity, suboptimization as a result of equipment changes, and measurement of system performance. The plan of work leading to a quantitative description of these study areas is based on the growing interest in total system design using simulation as an analytical method (Manula, 1963). CHARACTERISTICS OF PRODUCTION OPERATIONS FROM ROOM-AND-PILLAR SECTIONS For a given mining method, raw production in a given section of a mine is primarily dependent upon the coal seam thickness, roof and floor conditions, methane emission, the mining methods, and the man-machine element. Average section production varies from 300 to 800 st per shift for conventional and continuous mining in high seams and from less than 100 to 300 st per shift in low seams. Since the reject varies from 0 to 40%, these figures must be decreased by the appropriate percentage to reflect the amount of clean coal mined. Personnel requirements per production section per shift for the various methods are listed in Table 1. Table 1. Production Personnel Method No. Method No. Conventional 12-1 5 Longwall 9-14 Continuous 9-1 2 Shortwall 9-12 MINING VARIABLES To evaluate the constraints and interrelationships for various mining methods, it is necessary to categorize the variables which underlie system production potential. Seven critical independent variables which determine production can be identified and categorized (Suboleski, 1978) : Seam Height The five categories are as follows: less than 36 in.;. 36 to 55 in.; 55 to 100 in.; 100 to 180 in.; and greater than 180 in. Floor Quality Floor quality ranges from : Excellent: Smooth, hard, grades less than 1 to 1 % % , and dry. Good: Smooth, soft but dry, with grades less than 3 % . The floor will deteriorate, but cautious operation can prevent it. There may possibly be heaving at some later time. Fair. Soft and damp. There is occasional interference with equipment operation; requires the use of four-wheel drive shuttle cars; ruts with regular use, and may have adverse grades of 5 to 7%. This may be coupled with slippery bottom and/or occasional steep rolls. Poor: Soft and wet. Requires blocking of the bottom to support equipment. There are frequent steep rolls and grades in excess of 7%. Roof Quality Roof quality ranges from : Excellent: Men are able to work under the unsupported top during the initial production cycle if legally permitted. Good: The roof is bolted on a 4 x 4 or 5 x 5 pattern with short bolts (442 in.) or <seam height if the seam >42 in., or requires posting with no bolts on a 4 x 4 or 5 x 5 pattern. There are no falls. Average: The roof is normally bolted on a 4 x 4 or 5 x 5 pattern, but with long bolts (>seam height or >6 ft.). There are infrequent minor falls or there may be an excellent roof which is difficult to drill. Fair: This type often requires spot bolting in addition to the regular pattern or bolting with planks. The roof conditions require shorter than planned cuts, or narrow cuts. Poor: This type requires bolts plus crossbars and posts, or installation of yielding supports or truss-type support. It is almost certain to fall if this is not done. Methane Liberation This ranges from none detected to low (no buildup at the face, even with minimum ventilation requirements) to moderate (the curtains must be extremely tight and tubing close to the face or methane will build up to 1 % during the loading of the car) to high (methane will build up to 170 if the miner is operated at the normal rate, even with proper ventilation). Hardness of Coal Coal hardness falls into the following categories: Soft: Soft coal is easily cut by a continuous miner. A plow could be used by longwall. Average: Coal of average hardness could be easily cut by a miner, and a shearer would be used in the longwall. Moderate: Moderately hard coal causes difficult cut-

Jan 1, 1982