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By R. M. Schuster, F. M. Benavides

Samuel G. Bonasso The article by Benavides and Schuster provides an in-depth study of three transportation alternatives for a four-mine complex in western Kentucky. The examination of aerial tramways was not undertaken as an alternative solution. We feel this is an oversight since industrial ropeways are competitive with both belt conveyance and overland truck hauling. In fact, there are aerial tramway systems, operational today, which are 100 years old and operating with some original components. Maybe unfortunately, there are no fixed rules or guidelines whereby the most cost-effective means of transporting and handling material for a given situation may be selected. Each situation must be evaluated so the variables that influence the selection of the desired alternative can be clearly defined. However, there are in-place industrial ropeway systems that have proven economically feasible over a range of 1.6-50 km (1-31 miles). The more difficult the terrain, the greater the cost efficiency.

Jan 1, 1983

By Bernard J. Steblay

Millions of mechanical anchor roof bolts are used each year for mine structural support. The benefit of this bolting depends on a number of factors including rock density, bolt length, in situ stresses, time elapsed between mining and installation, rock properties, bolt patterns, and tension (Lang, et al., 1979). Installation tension is a major determinant of support quality. Postinstallation tensions indicate both the usefulness of the individual bolts and the behavior of the reinforced rock structure. The importance of short- and long-term bolt tension measurements is well recognized, and such measurements are required by regulations (Fed. M/NM Nine Safety and Health Reg.). These regulations also take into account the difficulty of practical tension measurements. Only a statistical sample of the bolts installed is required to be measured using current torque wrench technology. Drawbacks to this practice are that the anchorage is disturbed and perhaps weakened, accuracy is limited by friction to about 30% (Lang, et al, 1979, and Barry, et al., 1956), and the procedure is relatively time intensive.

Jan 1, 1984

By James W. Martin, Robert R. Faddick

INTRODUCTION Virtually every sector of society in our country feels the impact of tunnels, either through the transportation of water, commodities, or people. The economic implications are staggering. The Committee on Rapid Excavation (1) reported that during the near future, 1968-1975, underground excavation activity will comprise 946 miles of tunnels (subways: 85 miles; underground urban highways: 123 miles; intercity highway tunnels: 210 miles; water supply tunnels: 528 miles) and 5,119 million tons of crude ore; metals: 874 million tons; nonmetals: 899 million tons; and coal: 3,346 million tons. It is estimated that the cumulative demand for underground excavation in the decade 1970-1979 will be 13 billion dollars for construction-oriented demand and 16 billion dollars for mining-oriented demand. The respective figures for the decade 1980-1989 are estimated at 22 billion dollars and 18 billion dollars. Of the many advantages claimed for tunnels (2, 3, 4, 5) the environmental considerations are becoming increasingly important. Transportation tunnels particularly for rapid transit systems, offer reductions in noise pollution and air pollution while improving aesthetics and optimizing land use (fewer problems of right-of-way and disruption of utilities). Considerable interest has been shown recently in sub-surface construction and mining (6, 7, 8). Recognizing the future demands for tunnels has led to considerable study of methods to improve rates of tunnel advance per day, safety, and the overall economics. The search for higher rates of advance has Led away from what has heap termed conventional methods (drilling

Jan 1, 1974

By Kazem Oraee

In underground coal mining, particularly room-and-pillar methods, the coal pillars play a significant role in roof stability. If the pillar dimensions are increased, the pillar bearing capacity also increases, but more coal remains in the pillar and therefore the recovery of mining operation decreases. Therefore, determining the optimum pillar dimension based on technical, economical and performance parameters is important. In this paper, the coal pillar is designed by using the concept of ground reaction curve (GRC). For this purpose, the GRC for coal pillars is drawn and then the elastic and plastic zone of coal pillar behavior is determined. Based on elastic and plastic zone, different equations are presented to draw a pillar reaction curve and the process of coal pillar design based on GRC is explained. As a case study, this new technique is applied to study the coal pillar state in Tabas coal mine of Iran. The results show that the presented new approach is successfully used in the design of the optimum coal pillar dimensions, and also determines the elastic and plastic behavior limit, which is important especially for the logical design of yield pillars.

Jan 1, 2009

By Everett H. Dobbs

The Tripoli deposits in the southwest corner of Missouri In Newton County and the northeast corner of Oklahoma in Ottawa County, located in the vicinity of Seneca, Missouri, contains an unusual and peculiar form of silica which has not been found any other place in the world. Its outstanding characteristic is the physical structure of the individual particle, The particle structure of the Missouri-Oklahoma type Tripoli accounts for its market. It is a soft, friable, porous, double-refracting silica of the chalcedony variety, The particle is porous, has a fibrous structure, no sharp edges or comers, ad an average size of less than .01 millimeter, It varies from 90 to 98 per cent Si02 with less than 1 per cent free silica in the form of quartz, 24; has ignition loss of 1 per cent and fractional percentages of iron, alumina, lime, etc.

Jan 1, 1960

By M. Visnjic

Open Pit Mine Production scheduling under commodity price uncertainty suffers from an exponentially increasing problem size as simulations and real options flexibility are used to generate and evaluate multiple production schedules. Robustness evaluation techniques attempt to evaluate a production schedule that is generated on a single set of economic parameters against several varying prices and sources of uncertainty. This approach is invalid as the corresponding optimal LOM mine plan will change for each set of evaluation parameters. Using commodity market futures and treasury bonds as production schedule economic input parameters provides fully price and time-value-of-money risked scheduling parameters that maintain a deterministic problem size. This paper will provide comparative analysis of project NPV’s coming from traditional price uncertainty evaluation based on a single fixed LOM mine plan using varying prices versus evaluation based on varying LOM plans that are both generated and evaluated using varying prices. When cross evaluating constant price mine plans against simulations, the upside potential and downside risk of a project are significantly misrepresented. INTRODUCTION The life of mine (LOM) production scheduling problem seeks to answer the question of from where and when to extract a given block within the ultimate pit limit as well as where and when to process it. Solving this problem takes into account the constraints of extracting any particular block while seeking to maximize the net present value (NPV) of the mineral asset as a whole. A direct driver of the value of a block, and there for the entire asset, is the market price of the commodity in question. Complications arise when an optimal production schedule is attempted to be solved under price uncertainty. Many solution methodologies have been proposed in an attempt to optimize under this criterion, yet there are three salient aspects that are overlooked during this process. They are: • Generating a single production schedule and evaluating it against many simulated price paths. • Failing to understand the mechanism describing particular commodity price behavior • Inappropriate risk adjustment In an effort to address these aspects of production scheduling under commodity price uncertainty, we propose a methodology to define the economic parameters as input that is applicable to most if not all production scheduling approaches. This methodology will not only simplify the production scheduling process in terms of establishing block value but utilizes the risk adjustment of real options valuation to avoid the arbitrary blanket risk adjustment of traditional discounted cash flow valuation. Our findings conclude that attempting to optimize around individual price paths is futile and using a market risk adjusted single price forecast provides a justified economic basis for production scheduling while maintaining the same problem size as a deterministic production scheduling problem.

Jan 1, 2019

By N. L. Dorset, K. L. Heasley

Unfortunately, mining and mining accidents have gone hand-in-hand since man first started to extract ore from the ground. In the first published treatise on mining, De Re Metallica, Georgius Agricola (1556) stated that cold, water, dust, stagnant and foul air, roof falls, falls from ladders and demons all caused injury and death in the mines of his day. Although demons are no longer considered a cause of accidents in modern mining, the other factors remain with us still. The United States government started keeping track of fatalities with the establishment of the federal Bureau of Mines in 1910. Successor agencies, such as the U.S. Mine Safety and Health Administration (MSHA) continue to track fatalities today. Looking at the records, it can be seen that coal mine fatalities dropped from 2821 in 1910 to only 27 in 2004. The reduction in fatalities and injuries didn’t “just happen.” It took concentrated effort from the entire mining industry: miners, supervisors, safety officials, mining inspectors and mining researchers. But first, specific hazards must be identified before they can be corrected. In past, coal mining accidents have been analyzed by: type (roof fall, electrical, etc), mine attribute (location, seam height, etc.), and aspects of the mineworker (work experience, job classification, etc). Much of this research helped to direct the industry’s attention to where additional vigilance and safety training was needed. No doubt this directed effort has led, at least in part, to the decrease in coal mining fatalities. This paper takes a novel look at coal mining fatalities: it examines the risk of fatalities based on how long the mine has been open.

Jan 1, 2006

By Luciano Ramos, Daniel Santos

Igarape Bahia Mine, which is currently the largest gold producer in Brazil, belongs to Companhia Vale do Rio Doce - CVRD and is situated 250 miles south of Belem, state of Para, Brazil. It came into operation in 1992 with the startup of the CIP plant, fed with high grade ore, presently at 3.4gAu/t. The ore is totally oxidized, containing extremely fine particles of free gold. The ore is soft and low cyanide consumer, with a maximum work index of 12kwh/sht. In 1993 a Heap Leaching Plant was set into operation, handling low grade ore of · 1.s g Ault. The Heap Leaching Plant has undergone two major expansions. In 1994 its capacity was raised from lMtpy to 2,2Mtpy and in 1998, with a thorough remodeling of crushing operations, it was raised again to 3.5Mtpy. The CIP plant, which was originally designed with a capacity for l. lMtpy of ore, was expanded to a 2.2Mtpy capacity in 1994. Presently, the CIP plant accounts for most of Igarape Bahia's total gold output, with approximately 220,000oz per year. Igarape Bahia's annual output is around 360.000 oz. Over the last three years, work has been intensified to improve performance of both processes, aiming at maximizing productivity of the two industrial plants. Reduced costs and increased revenues have been given a special emphasis in the unified improvement program. Cost · reduction has involved developing methodologies to rationalize consumption of materials and inputs, while increased productivity has been given top priority as a means of generating increasing revenues. Thus, all of the improvement and development efforts have had a common goal: to increase operating income.

Jan 1, 2000

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 John Neale, Robert Huberts, Tony Pinches

A major R&D programme for the application of bacterial oxidation to the pretreatment of refractory sulphide gold ores was started at Mintek in the early 1980s. This arose from an established expertise base in the bacterial leaching of base-metal sulphide ores. The refractory gold programme has been supported by a number of South African gold-mining companies, but major support has been provided by the Anglo American Corporation of South Africa (AAC) and the AAC Vaal Reefs Exploration and Mining Company Limited · (Vaal Reefs). The Mintek-AAC collaboration has been formalized as a joint-venture technology agreement for the comme;cialization, as well as continued development and improvement, of the bacterial oxidation process (MINBAC). From a process standpoint, bacterial oxidation involves the contacting of slurries of finely ground sulphide concentrate with suitable strains of iron-sulphur oxidizing bacteria, which act as the catalyst to promote sulphide·· oxidation by oxygen from air. Process engineering is simplified in that this reaction is carried out at low temperatures and ambient pressures. The view was taken that the successful development and implementation of the MINBAC technology should be based on parallel R&D aimed at an understanding of the process fundamentals, the process engineering and scale-up requirements, as well as the ancillary requirements for the gold recovery-processes and environmental management. This has represented a major R&D effort at a total cost to date of around US $10 million.

Jan 1, 1993

By Kewal K. Kohli, Richard E. Thill, Syd S. Peng

The results of unpublished investigations into surface subsidence from coal mining in the Northern Appalachian Coalfield are summarized. These investigations were carried out by various coal companies and the State of Pennsylvania in the sixties and seventies. Subsidence data were collected and analyzed from 10 room-and-pillar panels in 5 mines in the Pittsburgh coal seam. Results show that angle of draw ranges from 26° to 33° and subsidence factor from 0.42 to 0.72; surface heating generally occurs beyond the edges of the panel, the amount and extent of which vary; waviness occurs in the subsidence profile if a substantial number of pillar stumps are left in irregular patterns; interpanel effect is significant; time-dependent subsidence exists, but varies for different panels; and surface slope does not seem to affect the amount of subsidence.

Jan 1, 1982

By V. Rajaram

R.K. Leininger, N.R. Hasenmueller, and D.D. Carr The content of the paper by V. Rajaram does not fulfill the expectations of the title. But Rajaram submitted the article in October 1983, and he could not have foreseen the numerous developments that would occur before his paper was published more than two years later. Nevertheless, Rajaram failed to mention the interest in oil shale development in southern Indiana beginning in late 1979 and continuing through the present as a result of special financial encouragement of three oil shale projects in May and August 1984 by the Indiana Energy Development Board and the Indiana Corp. for Science and Technology. A session at the 1985 Eastern Oil Shale Symposium in Lexington, KY, Nov. 18-20, 1985, gave the current status of oil shale developments in the eastern United States. Speakers at this session reported on the three Indiana projects. First, Gary D. Aho, Cliffs Engineering Inc., spoke on a feasibility study by Cliffs Engineering and Allis Chalmers for a site-specific pilot plant using the Allis Chalmers process. The plant site is in Clark County, IN, on property of the Midwest Energy Resources Co. The project is funded by $240,908 each from the Indiana Energy Development Board/Corp. for Science and Technology (EDB/CST) and the US Department of Energy (DOE) and $120,454 from the corporate sponsors (total $602,270). Completion is scheduled for mid-1986. Next, Edwin M. Piper, Stone and Webster Engineering Corp., discussed the American Syn-Crude/Indiana Oil Shale Project. This effort followed the completion of two smaller projects funded by the Indiana EDB/ CST: "Testing of Indiana Oil Shale in a Petrosix Pilot Plant" (total funding by EDB/CST at $50,000) and "Assessment of the Petrosix Process for an Indiana Shale Oil Plant" (total funding by EDB/CST at $100,000). The status at the time of the report at the Oil Shale Symposium was that a request for an extension of time for securing nonfederal support had been submitted to the US Synfuels Corp. The proposal included building an 11-m (36-ft) diam retort in southeastern Indiana to process the New Albany Shale and to produce 366 m3 (2300 bbl) of shale oil per day by the PETROSIX process. The Indiana EDB/CST had contracted with Stone and Webster at $401,100 from EDB/CST and $245,835 from Stone and Webster for activities to advance the project in the negotiations with Synfuels Corp. At the time of the report, this project was the only eastern oil shale proposal that was still on the agenda of the Synfuels Corp. As a result of Congressional action in late December 1985, federal support from the Synfuels Corp. is no longer possible. Finally, Victor H. Carr, Eastern Shale Research Corp., described his firm's project, which is jointly supported by DOE ($227,749) and the Indiana EDB/ CST ($73,850) and is entitled "Feasibility Study to Determine Suitability of an In-Situ Process to Recover Hydrocarbons from Eastern Shale." An area in Scott County, IN, had been chosen, but not a specific 9 x 15-m (30 x 50-ft) site. One burn of a small in situ retort is contemplated as part of the project. Besides these three projects, several reports on shale research were presented. Joseph Damukaitis, American Syn-Crude Corp., reported that a pilot plant using the hydrogenation-extraction (H-E) process (described at the 1984 Eastern Oil Shale Symposium) was 94% built and would go through shakedown with oil shale but would then shift mechanical devices to process coal mine waste. Current status of research on the HYTORT process was then presented by Raymond C. Rex, Jr. Oil shale beneficiation research at the University of Alabama/Minerals Research Institute was reported by R. Bruce Tippin. Scott D. Carter discussed continued research on fluidized-bed retort¬ing of shale at the Kentucky Center for Energy Research Laboratory. Carl E. Roosmagi of DOE, Morgantown, reported on the oil shale research at the Morgantown Energy Technology Center (METC) laboratory. Henry J. Gomberg, Ann Arbor Nuclear Inc., discussed "Radiation Combined with Donor Solvents for Extraction and Up-Grading of Kerogen." Aurora M. Rubel and coauthor Eileen Davis presented results of research at the Kentucky Center for Energy Research Laboratory under the title "The Effect of Shale Particle Size on the Products from the Bench Scale Fixed Bed Steam Pyrolysis of Kentucky Sunbury Shale." Lastly, Maria Rockwell, Technical University of Nova Scotia, presented "Processing and Up-Grading of Low Grade Nova Scotia Oil Shale for Potential Use." A review of shale oil prospects by Gerald Parkinson in Chemical Engineering for Feb. 3, 1986, covers both western and eastern projects and includes a report that the US DOE is funding a few relatively small projects; most of the fiscal 1986 budget of $12 million for shale oil is for fundamental research. Projects include a $3.2 million three-year contract with Hycrude Corp. (Chicago) for development of the HYTORT process and a $1.2 million three-year contract with the University of Alabama's Mineral Resources Institute on beneficiation of eastern oil shale by froth flotation. The report incorrectly states that current projects include a total investment of $466 million in a pair of 18-month technical and economic feasibility studies for proposed projects in southern Indiana. The correct figure is $468,657 [$240,908 for the Cliffs Engineering/

Jan 10, 1986

By Chuang Sun, Feng Luo, Guo‑dong Li, Xue‑qing Li, Tuan He

The mining-induced failure of the coal seam floor is essential for water inrush. The mining disturbance to the floor, especially in the thick coal seam, is severe, and the water inrush risk is also higher than that in regular thick coal seam excavation. The superposition of many stresses, including in situ stress, mining-induced stress, and confined water pressure, must be considered in the prediction of the floor failure depth. This study adopted the elasticity analysis, FLAC3D numerical simulation, and on-site acoustic wave test comprehensively. The thick coal seam working face of the Zhong-Yu coal mine affected by confined water was selected as the engineering background to study the characteristics of the floor failure. Based on elastic foundation theory and the superposition principle, the mechanical model and the failure depth criterion of the floor were established, respectively. The distribution and evolution of mining-induced stress and the plastic zone in surrounding rock during the mining process are obtained by FLAC3D. In addition, the changes in the P-wave wave velocity in the floor before and after mining were compared and studied by the acoustic wave test method. The range of floor damage depth is determined on the basis of the above research.

Jun 8, 2022

By Roberto Pimentel de Souza

CURD started producing pellets in 1969, with one two-million ton straight grate plant. In the beginning of April '73, the second unit came on stream with an additional capacity of 3 million TPY of pellets. In January '77, the third unit started, bringing the annual capacity to 8 million TPY. For the present year 3 more units, 3 million each, are expected to begin production. CVRD's experience is given about the use of different binders and additives. Over the years several kinds of pellets have been produced to satisfy the market requirements. General quality information is given regarding each.

Jan 1, 1978

By D. C. Hogeman

Growing Greener is the single largest investment of state funds in Pennsylvania’s history, allocated to address the Commonwealth’s critical environmental concerns. Signed into law by Governor Tom Ridge on December 15, 1999, Growing Greener will enable the Department of Environmental Protection (DEP) to appropriate nearly $240 million over five years, to watershed restoration and protection, abandoned mine reclamation, and oil and gas well plugging projects. DEP has utilized these allocations in some remarkably innovative ways, as it: involves the cooperation of several state agencies, local governments, and grassroots organizations to address environmental concerns of the Commonwealth, provides funds directly to watershed groups based on locally determined decisions for local watersheds and offers a user friendly process. In three years, over $130 million in watershed restoration and improvement projects have been initiated.

Jan 1, 2002

By Y. J. Wang

The use of controlled recirculation began in the early 1930s. Although this method has been applied in many mines since then, a generalized comprehensive network analysis is still lacking. This paper presents a unique approach in which the ventilation network with a controlled district recirculation is divided into two subsystems: a main subsystem and a recirculation subsystem. The subsystems are analyzed individually, and the results and their relationships are then integrated into discussions of the total ventilation system. The analysis of the recirculation subsystem is facilitated by introducing a nondimensional parameter (A), which represents the ratio of the air quantity for the working face to that for the subsystem. As a result, far and regulator pressures and air power for various recirculation arrangements can be effectively expressed as a function of and the subsystem air quantity. Numerical examples are included.

Jan 1, 1997

By Tim Neil, O&apos

The coming years should see moderate growth in the US coal industry. That growth may come at the expense of the oil and natural gas industries. Conoco pegs coal growth at 2% a year, until the year 2000. During that same period, Conoco projects only 0.5% annual oil growth and "a flat or negative trendline" for natural gas. This is compounded by the fact that coal has a delivered cost per Btu that is only half as much as it is for natural gas and only a third as much as it is for oil. So said Ralph Bailey to many of the 2600 attending the opening session of the American Mining Congress Coal Convention, May 12-15, in Pittsburgh, PA. Bailey is chairman of the AMC. He is also chairman of Conoco. While coal's projected growth is not spectacular, "it is in fact almost an assured growth," Bailey said. Weak oil and gas prices will likely prevent faster growth for US coal. Most of coal's increased demand will come from the electric utility industry and expanded steam coal exports. Conoco's study projects that domestic coal demand will be strengthened in the 1990s. By then, the present surge of nuclear power plant constuction will be over. And there will be a lack of acceptably priced, large-scale generation alternatives for utilities. "It is not likely that any electric utility is going to be ordering new nuclear reactors," Bailey said. "And as oil and gas supplies become scarcer and more costly, it is only logical that coal is going to fill the gap." At the same time, Bailey believes the US coal industry must find ways to lower its costs. He said cost excesses can be found in "regulatory overkill, labor, and simply bad habits" hidden by years of high inflation. "Those costs have now been laid bare, because we are going through a pe¬riod of disinflation. We have to put our house in order, particularly if we are going to compete in world markets." Bailey also touched on coal research. "The industry certainly accepts the fact that we must find a way to burn coal as cleanly as possible. A lot of work in that regard is going on. I expect there will be some significant break-throughs." Bailey said the coal industry is being squeezed this year. Last year, coal customers accumulated inventories in anticipation of a major coal strike that never materialized. Now, many utility customers are working down these inventories. So they are not taking deliveries on their coal contracts. But coal use is up in 1985, compared with 1984, Bailey said. So increased coal use, along with supply drawdown, should strengthen the coal market before the year is out, he said. After Bailey's presentation, some 100 speakers addressed policy and technical topics at 15 sessions during the four-day meeting. It was the first time since 1977 that the AMC Coal Convention has been held in Pittsburgh. And this year's attendance was up 40% from the last AMC Coal Convention held two years ago in St. Louis, MO. This year's registrants included 228 companies, 225 manufacturers, and 106 associated members. The only negative was the David Lawrence Convention Center. It was less than ideal. By turns, meeting rooms were too small, too cramped, or too far from one another. The session on longwall mining was so crowded that the doors were propped open so conference delegates could peer in. A concurrent manufacturers' forum session needed 50 more chairs to accommodate those wanting to attend. However, on to summaries of some of the presentations. Coal transportation and export Since Congress approved the 1980 Staggers Rail Act, railroad rates for hauling coal have not been excessive. In fact, rail rates for coal have increased less than 0.5% a year, in real terms, since 1980. Moreover, the market oriented principles written into Staggers are contributing to the improved financial and operational health of the nation's railroads. But no railroad is earning excessive profits. That is the gist of a coal transportation study being completed by the US Department of Energy. William Vaughan is DOE's assistant secretary for fossil energy. He affirmed the thrust of the upcoming report. Vaughan did allow that Interstate Commerce Commission (ICC) regulations on rate reasonableness could permit the railroads to exploit their monopoly power on captive shippers. Luncheon comments later made by Don Hodel confirmed Vaughan's comments on railroad rate justification. Hodel is Secretary of the

Jan 7, 1985

By Simon D. Handelsman

Technical co-operation activities of the Department of Technical Co-operation for Development of the United Nations Secretariat have included the introduction of electronic data processing techniques in mineral sector projects for several years; computers have been provided to countries in Africa, Asia and Latin America. Advisory services are provided to interested developing countries at their request concerning applications for various uses in mineral sector activities. They include advice on appropriate hardware and software depending upon the requirements of the particular Government. The Department's activities in this area are described. The input from a Group of Experts on this subject convened by the United Nations, and their conclusions and recommendations, are also discussed.

Jan 1, 1986

By James C. Hower, B. K. Parekh

Introduction The purpose of coal preparation is to improve the quality of coal to make it suitable for a specific purpose by (1) cleaning to remove inorganic impurities; (2) sizing-crushing or screening, or both; and (3) special treatment, such as dedusting. The properties and quantities of impurities in coal are of major importance in the design and operation of steam generating equipment. Although boilers are often designed and equipped to use a wide range of coals, no boiler will perform equally well with all types of coals. All coals have certain properties that place limitations on their most advantageous use. These limitations are especially stringent for many of the older installations. Because of a general lowering of quality of raw coal in recent years, the need for coal cleaning has significantly increased. Among the factors contributing to the need for increased coal preparation are (1) increased demand for quality brought on by market and environmental requirements; (2) increased extraneous dilution caused by mine, health, and safety laws; and (3) depletion of the higher-quality coal seams. The major characteristics of coal and impurities from the standpoint of mechanical cleaning are particle size composition, generally called size consist; density differences; the relative friability of the coal and its associated impurities; hardness; and strength. Some of the other factors related to preparation are petrographic composition and rank. RANK CLASSIFICATION Coal is a general designation for a great number of solid organic minerals with different compositions and properties; all are rather rich in carbon and have a dark color, generally black. Next to mineral oil and kerogen, coal is the most important reservoir of carbon in the world. Carbon is an indispensable necessity of life as well as the main source of energy. Coals are found in stratified deposits, sometimes at great depths. All coals owe their origins to slow decomposition and chemical conversion of immense masses of organic material. As found in seams, coal is a heterogeneous mixture of organic and inorganic materials. Not only are there large differences in the properties of coal originating from different seams, but also in coal removed from different locations in a single seam. A genetic relationship exists between peats, brown coals, lignites, biturninous coals, and anthracites. As a whole, the process of coal formation, or coalification, proceeds as a continuous transformation of plant material, each phase characterized by a degree of coalification, or rank. As a measure of this rank, the carbon content or some related parameter can be used.

Jan 1, 1991

By Anna Marabini

This paper provides a summary of the studies performed over a period of more than fifteen years by the Italian National Research Council's Mineral Processing Institute in Rome to develop applications for the use of chelating reagents in the flotation of metallic minerals. A description is given of the various phases through which the studied progressed, starting with the combined use of commercial chelating reagents and a neutral oil and then moving on to the synthesis of new long-chain chelate collectors for the flotation of sulphide and oxidized Pb, Zn and Cu minerals. After a series of preliminary tests which confirmed the possibility of floating various metallic minerals with commercial reagents containing chelating groups exerting specific action on given cations, the studies were addressed to the development of a theoretical method of choosing chelating groups that exert selective action on one metallic mineral rather than others. The theoretical approach was based on thermodynamic data concerning the chemical equilibria in solution. The validity of the method has been proved in numerous cases by flotation tests on pure minerals. Subsequently the research was directed towards the design and synthesis of reagents with a mixed aliphatic-aromatic structure containing chelating groups for Pb and Zn and an alcoxyl chain of various length, position and configuration. The flotation results obtained on oxidized and mixed Zn-Pb ores provided interesting pointers for designing the nonpolar portion. The structural criteria identified via these studies were interpreted on the basis of chemical and steric considerations. A description is given of a new synthetic chelate collector which is effective in the selective flotation of Cu minerals from complex sulphides. The fact that this reagents is more selective than xanthate is demonstrated by comparative flotation tests on actual ores.

Jan 1, 1994