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By Wojciech Suwala

The transition from centrally planned to market economy affects methods of economic analysis. The models which were used in the past are riot valid presently, however they we're the seed which initialized the development of methods and applications. There is more than twenty years of experience in modeling of coal mining development. The first attempts were devoted to select the moment of mine construction commencement in order to meet planned output. In Poland significant development of such models began in 1986. Within the Central Research and Development Program there has been a continuous development of models. These models from econometric to optimization ones, were a certain sequence which, in accordance with changing economy system, led to the last version of the model. It is the most suitable one for contemporary problems of coal mining in present Polish circumstances.

Jan 1, 1992

By D. J. Simbi, T. R. C. Fernandes, M. Nyamhunga

The recovery of P2O5 from a 90-95% minus 45 microns phosphate slimes sample was carried out in a 5.08-cm internal diameter and 549-cm high flotation column cell. The influence of the feed rate, feed percent (%) solids, and frother dosage on the recovery was investigated following a truncated cubic 3 level by 3 variables experimental design. Two three-variable interactions of feed rate (-l)/feed percent solids (+l)/frother dosage (-1) and feed rate (-l)/feed percent solids (-1)/ frother dosage (+I) gave the region of optimum column performance: recovery (52.60-74.50%), mass yield (15.68-18.80%), and concentrate grade (22.87-31.2196). The collector dosage also showed a significant influence on the column performance. The high reagent consumption relative to the current plant levels points to the need for the removal of ultrafine particles (<10 µm).

Jan 1, 1999

By Russell K. McFarland, Eugene L. Foster

INTRODUCTION The U. S. Department of Transportation has underway an important new program which will have a major impact on rapid excavation technology. The Transportation Tunneling Program, as it is called, is a coordinated, multi-modal research and development effort. Its goals, if realized, will significantly improve our ability to build the underground structures needed for transportation. This, in turn, will improve transport efficiency, environmental impact, and the energy consumption associated with the movement of people and goods. Tunneling technology research and development had its beginning at the Department of Transportation in the Office of High Speed Ground Transportation (OHSGT). The OHSGT developed and implemented a program in 1965 to provide the technology for underground construction needed to support future high speed ground transportation. In 1967, when the OHSGT was transferred from the Department of Commerce to the Federal Railroad Administration (FRA), the program accompanied that office. The thrust of the FRA program has been cost reduction through the development of new materials, innovative designs, and better construction methods. During the late 1960&apos;s and early 1970&apos;s, other developments were underway which would influence the future of tunneling research at the Department of Transportation. An ad hoc

Jan 1, 1974

By D. M. Muir

Thiosulfate offers a nontoxic alternative to cyanide for processing gold ores. The mechanism of leaching gold using ammoniacal thiosulfate solution is driven by the Cu(II)-Cu(I) redox couple and is complicated by competing ligands such as NH3 and S2O32; It is shown that an understanding of the copper speciation and sulfur speciation is required to optimize this system. This paper presents Eh-pH and speciation diagrams for varying concentrations of Cu(II), S2O32- and NH3 and discusses the conditions under which various copper and sulfur species are stable.

Jan 1, 2002

By Phil D. Newman, Robert J. Pine, Kevin Ross

The Stratoni Operations in northeastern Greece rely on a selective backfill method to exploit high-grade lead-zinc deposits. Underhand cut and fill often results in spans approaching 6-9 m (depending on the mining method employed) and a competent backfill is required to avoid dilution problems. Cement consumption represents a significant mining cost and through improving the control of the backfill batch preparation, the cement content could be greatly reduced without jeopardizing the grade control. A new distribution system was installed and a QAIQC system designed in cooperation with the operators to allow a wide range of backfill recipes, providing cost savings to the mine. A review of possible failure modes and the consequent strength required for the chosen mining method was also completed and indicated potentially significant cement content reductions. The calculations are supported by 12 years of experience at the mines which provides a valuable insight into the applicability of the approach developed.

Jan 1, 2001

By V. Rajaram

A mine fire or roof collapse may necessitate the reversal of main fans to isolate the fire or provide an escapeway. Hence, to assist the mine operator in estimating the flow and pressure during reversal, Engineers International Inc. conducted a laboratory and field study of the reverse performance characteristics of main mine fans. Laboratory tests were performed using a 2.4-m (96-in.) diam vane axial fan to establish the forward and reverse performance characteristics under controlled conditions. Subse¬quently, a field test was conducted in a Colorado oil shale mine during which two 2-m (79-in.) diam fans were reversed. The data obtained indicate that reverse performance characteristics depend on the blade angle and the hub-to-tip ratio. The quantity in the reverse mode ranged from 30% to 65% less than in the forward mode, and the static pressure was directly proportional to the square of the quantity.

Jan 1, 1987

By N. R. Paterson, D. A. MacFadyen

A late-1980 airborne EM/magnetic method test over the State Line kimberlite area of Colorado-Wyoming shows weak but recognizable anomalous responses to the known pipes. The magnetic survey indicates the presence of several shallow subsurface bodies adjacent to the known kimberlites, which are interpreted as possible blind diatremes. The survey data, in profile and contoured map form, has been correlated with geological map information available at the time. It can serve as the basis for reexamining kimberlite distribution in the area, taking into account geological findings during the recent work on known bodies.

Jan 1, 1987

By R. F. Al-Fariss

The phosphoric acid industry is expected to develop in Saudi Arabia in the near future. There are three main reasons for expecting this: the discovery of phosphate deposits in the Sirhan-Turayf region, the construction of phosphate fertilizer facilities of the TSP, DAP and NPK plants on the east coast of the country, and the availability of an ample amount of sulfur As a by-product from the petrochemical industries. This study is a part of the research work performed in the chemical engineering department At King Saud University to evaluate the Saudi phosphate rocks for the wet process phosphoric Acid production and to test different flotation methods for the carbonate rich phosphate rock In a laboratory scale flotation cell. Experimental results for the above tests, as well as Beneficiation by calcination, are presented.

Jan 1, 1993

By C. J. Bise

Continuous mining accounts for about 69% of the nation&apos;s underground coal production. This level is not expected to change much in the near future. This is because continuous mining represents the primary means of under- ground coal production. It is also the primary means of driving development entries for underground coal mines, including longwall mines. The continuous miner worksite contains many characteristics that can lead to personnel accidents. It continues to be an area of concern for mine managers, safety engineers, and training coordinators. In an effort to assist mine management in attempts to reduce the number of accidents and injuries sustained in this area, this paper presents a loss-control-based, non-intrusive strategy for conducting safety evaluations at continuous miner worksites.

Jan 1, 1991

By Edward F. Fries

Computerized, real -time monitoring had its beginning in the U.S. coal industry in the early 1970&apos;s. Over the last 10 years, developments in technology have made systems available that are capable of monitoring and controlling many mine parameters that can increase safety and production. However, situations currently exist where computerized monitoring systems are not being utilized to their fullest capability. They produce reams of printed output that are not sorted in a useful format, and human operators are not able to react fast enough in emergency situations tn tile large amount of information that the systems generate. A solution is the application of an expert system as the interface with real-time monitoring. An expert system would use an extensive knowledge base and human-type reasoning ability to make decisions on optimum strategies. Expert systems have been applied successfully to problems in other industries, and could provide significant benefits to mine information management systems. The use of an expert system with real-time mine monitoring is discussed in this paper.

Jan 1, 1986

By Peter T. Luckie, Mark S. Klima

INTRODUCTION A physical separation partitions a stream of particles into two streams - one containing a concentration of a desirable constituent; the other containing a defficiency - on the basis of a difference in physical properties. Separating ores into concentrates of increased grade and gangue minerals has been practiced for thousands of years. Physical properties of materials which have been used to achieve separations include size, relative density, shape, magnetism, surface charge, color, characteristic emission, resilience and strength. The study of physical separations has also been termed attribute tracking. The term attribute is used to describe the content of the material of interest, or, sometimes, properties not used as a basis of the separation. The content is usually given by its assay; e.g., %Cu, %Fe, etc. Attribute tracking involves material balancing. For a separation using two physical properties, say x and y, the balance is

Jan 1, 1986

By Robert J. Wise, Mark Alspaugh

Underground longwall coal mines depend on conveyor haulage to transport large volumes of coal from the longwall face conveyor to the mine portal. In the last few years, the need for longer and larger longwall panel conveyors has become very significant. In order to keep conveyor equipment to a minimum and still transport higher tonnages over longer lengths, intermediate drive technology has been developed. The use of DC motors and controls in conjunction with load sharing techniques have a1 so proven effective. A case study of a new longwall panel conveyor at Utah Fuel&apos;s Skyline Mine incorporating these design techniques will be presented.

Jan 1, 1993

By Michael F. Tucker

Dealing successfully with intercultural issues is critical for success on an international assignment. This is true not only for employees but for the accompanying spouses and children as well. This paper presents a set of research-based competencies required for successful life and work in another country, such as open-mindedness, flexibility, and respect for the beliefs of others. Best practices for training employees and their families bound for international assignments are also presented.

Jan 1, 2001

By John R. Marks

The first 0.7 m3 (1 cu yd) diesel load- haul-dump vehicle (LHD) arrived at the Homestake Gold Mine in Lead, SD in I969 to muck a ventilation drift. Others soon followed. Mechanization has subsequently changed stoping methods, manpower requirements, ventilation practice, the definition of minable reserves, and it has impacted safety and health. These have all had a direct bearing on the economics of producing gold ore from deep underground. Mechanized mining Before mechanization, production quotas at Homestake were met by several open cut-and-fill (OCF) mining methods. OCF mining relied on jackleg and wagon drilling, electric and compressed air slushing and cribbed raises brought up through the fill. Even square- set stoping was used until about eight years ago. The mine became 100% mechanized in 1988. The two current stoping methods are mechanized cut-and-fill (MCF) and vertical crater retreat (VCR). In 1992, MCF accounted for 54’S, VCR for 44% and development/uphole for 2% of the 1.4 Mt (1.55 million st) of underground ore produced. These methods are typically ramp- based and use diesel-powered LHDs, trucks, pneumatic drill jumbos and utility vehicles. Electric LHDs and rubber-tired compressed air muckers have also been used in VCR scrams. Pfarr (1991) and Mitchell (1980) provide good overviews of current production methods.

Jan 1, 1993

By John Chapman, Daryl Hockley, Michael Paul, Silvia Jahn

As part of the waste characterisation program to address site reclamation, WISMUT GmbH initiated 56 columns operated as large-scale humidity cell tests. The columns were initiated to assess the acid generation characteristics of waste rock from 14 waste rock piles distributed around the site. Of the 56 tests, 11 are ongoing and have been operational in excess of 160 weeks. The results to date from these long-term tests are surnrnarised. In particular, the methods for, and importance of, establishing the availability of the carbonate neutralisation potential and acid generation potential respectively, are discussed. Geochemical controls on uranium, and the conformity between the geochemical models MINTEQA2 and EQ3/6 in assessing these controls are discussed. Testing indicates that waste rock with an MS-NP:AP ratio in excess of about 2.7 should result in net neutral pH conditions.

Jan 1, 2000

By M. C. Roberts

To assess the future markets for a mineral from a producing district, the following three aspects must be considered: the future growth of the markets, the competitiveness of the district in terms of production costs and reserve adequacy, and the competition from alternative sources of supply. This paper focuses on the first issue by developing a method for predicting the demand for phosphate from trends in the major market for phosphate products, the fertilizer and agricultural market. The paper shows how broad changes in this end-use market for phosphate has evolved over time. These trends are then projected into the future to make an assessment of future phosphate requirements.

Jan 1, 2000

By D. R. Nagaraj

The practice of nonsulfide minerals flotation can be best characterized as an evolutionary blend of scientific theory and art. Although extensive fundamental studies have been carried out in the past several decades, and significant theoretical aspects have been developed, plant practice has developed the art form, often ahead of the theory, which is somewhat in contrast to sulfide minerals flotation. Several excellent review articles have been published in the past highlighting both the theoretical aspects and plant practice. An overview of nonsulfide flotation is presented here. Major differences in sulfide and nonsulfide flotation are highlighted. An assessment of the state of nonsulfide flotation, recent advances made in flotation processing, and industry needs are also given.

Jan 1, 1999

By Y. K. Yen, J. D. Miller, C. L. Lin

Particle size segregation is a common phenomenon in many particulate processes and has many undesirable effects. The size segregation which occurs on a belt conveyor causes a serious problem for on-line particle size measurement using image-based techniques. Whether particle size distributions measured from the top layer of the belt are representative of the total particle population is largely dependent on the degree of size segregation. Therefore, it is important to understand the nature of such size segregation in order to make appropriate corrections for on-line particle size analysis. Monte Carlo simulation has been used to provide segregation information on particles with simple geometry and the results can help to determine important factors in experiments with irregularly shaped particles. It is expected that the relationship between the particle size distribution of the top layer and that of the entire particle population on a belt conveyor can be formulated as a model based function.

Jan 1, 1997

By Ernest Peters

To model the zinc pressure leach, equations have been written that describe the rates of individual reactions taking place, including (a) oxygen mass transfer, (b) ferrous oxidation by dissolved oxygen, and (c) ferric reactions with ZnS and other minerals. In the continuous process, at steady-state, these take place at the same rate, and so the equations can be solved simultaneously. Model calculations using simultaneous equations are shown in graphical form to demonstrate the effect of different variables on the leach performance.

Jan 1, 1993

By J. D. Miller, D. M. Catarious, F. L. Stanley

The quality of cleaned products from coal preparation plants is often variable due to natural fluctuations in the washability characteristics of the plant feed. To combat this problem, many modern plants have installed on-line analyzers that provide feedback for the real-time control of product quality via the adjustment of circuit cutpoints. Unfortunately, optimization studies show that this approach may actually lead to increased losses of saleable coal. This paper discusses the problems associated with the real-time manipulation of circuit cutpoints and suggests alternative modes of operation that are better suited for plant optimization. A case study involving an eastern U.S. coal plant has been used to compare the economic impacts of these different approaches for plantwide control.

Jan 1, 2000