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By S. K. Kawatra, S. J. Ripke

Iron ore concentrates pellets are currently in duration heat hardened (sintered) under oxidizing conditions. Pellets produced from magnetite ore concentrate are completely oxidized during induration and finish as hematite pellets. These pellets then require a blast furnace to reduce the hematite to metallic pig iron. Partially reduced pellets would save energy and fuel during transportation and further reduction. It has been stated in the literature “the most important single factor responsible for the development of strength in fired magnetite pellets containing no additive is the oxidation of the magnetite to hematite and the subsequent recrystallization and grain growth of this constituent.” However experiments shown in this paper reveal that oxidation is not necessary to produce high-strength pellets. Magnetite concentrate pellets developed similar strength when indurated at 1350°C under either oxidizing (air) or inert (argon) atmosphere; the pellets sintered under argon remained magnetite. In addition, magnetite concentrate pellets indurated under reducing (CO) atmosphere also remained as magnetite, but required induration temperature of approximately 150°C less than the other pellets.

Jan 1, 2003

By Evangelos Spyridonos, Thomas Frommer, Wolfdietrich Skala, René Prissang

Operational grade modelling is a technique that uses production data to run daily updates of property models. It will enable mining engineers to use property predictions based on the most recently acquired data as support for quality control and decision making. The approach necessitates that the properties of the run- of-mine material can always be attributed to individual mining blocks or charges. The software employed must be highly reliable, because a system failure or the loss of data could seriously affect the mine's quality management. An operational grade modelling system has been developed for the Breitenau magnesite mine. It makes use of the Linear Octree Based Property Modelling system which was conceived and realised at the Free University of Berlin. This paper describes the system design and gives an account of the experiences during the first six months since system start-up.

Jan 1, 1996

By Fred H. Seymour

In spite of the progress made by geostatistical theory over the years, evaluation of low grade open pit gold deposits continues to be challenging. Many Carlin type deposits are modelled from exploration drilling spaced on 10C foot centers. From these drill holes, 50 by 50 by 20 foot blocks containing about 4000 tons of material are estimated. The block size is a compromise between being large enough for a good geostatistical estimation and being small enough for practical pit limit analysis and mine planning. Most of these gold deposits are highly variable and include ore and waste zones that are too small to be properly defined from exploration drilling information. Because of this, selective mining is controlled by sampling closely spaced blast holes where the density can be as high as 50 blast holes per exploration drill hole intercept. Figure 1 illustrates an example of the ore/waste contact definition before and after blast hole sampling. With exploration information only, a tentative ore/waste contact can be drawn between the exploration blocks.

Jan 1, 1989

By L. Lichty, R Bhappu, R. Rowan, G. Ramadorai

Treatment of refractory gold ores containing arsenic have always presented a major problem in their processing to recover the contained precious metal values. The major difficulties are concerned with lower recoveries, production of hazardous fumes, effluents and residues. Because of'these arsenic related problems, many otherwise economically attractive precious metal deposits and dumps all over the world are not exploited. In recent years, treatment processee for refractory gold ores and concentrates have been explored and a few commercial operations employing roasting or pressure leaching have resulted. Roasting has limitations due to environmental constraints related to off gases. Pressure leaching involving high temperatures (180% to 200%) and pressures (400 psi) is accompanied by high capital and operating costs. An alternate route to roasting for treating pyrite and arsenopyrite ores and concentrates ia the "lime-oxygen hydromet" process carried out at a moderate temperature (100%) and pressure (100 psi). A simplified process for treating such arsenic containing ores and concentrates utilizing low temperature and pressure oxidation is presented. This low cost treatment with compressed air and lime renders arsenic as an inert component in the residue, meeting all the requirements of the EPA Toxicity Test. The precious metal values are then extracted from the autoclaved residue by standard cyanidation. This paper discusses this new development.

Jan 1, 1990

By G. E. McClelland

In recent years exploration and development of low-grade sulfide precious metal ore deposits has increased. Low- grade ores are usually processed using conventional heap leach cyanidation methods. The potential for acid mine drainage from spent sulfide ore heap leached residues remains a concern even though the processed residue is stacked on an impervious liner system. It is therefore of critical importance to evaluate methods for long term prevention of acid mine drainage from sulfide heap leachable ores during the precious metal recovery process rather than mitigation during the closure and reclamation phase. This paper discusses two simple AMD prevention options for the recovery process phase. Laboratory evaluations were made using a modified humidity cell kinetic AMD test method on two low-grade sulfide ores without addition of an alkaline component and on the same ores with natural limestone or acid neutralizing oxide ore blended with the feeds before kinetic testing. Laboratory results are discussed in detail and demonstrate that blending an acid neutralizing component with sulfide ore effectively prevents the production of acid from the processed residue.

Jan 1, 1996

By J. J. Lewis

In the mid-1970's a major new prospect was proved in a previously unworked region of North East Leicester- shire, United Kingdom. Preliminary estimates from borehole information showed over 500 million tonnes of recoverable reserves. A special Planning Team was set up, to co-ordinate the work for the two local Areas, South Nottinghamshire and South Midlands (management of production of the UK National Coal Board is organised in twelve such Areas). The team was led by one of the authors as Deputy Director, Mining, North East Leicestershire Prospect (NELP). The remit imposed by the National Coal Board was to analyse the possible options of number, location and eventual rates of output of shaft or drift access; to select a recommended alternative in the light of geological, mining, topographical and environmental considerations; and prepare submissions in accordance with standard Board practice on major projects - such submissions including detailed engineering design, financial appraisal, and full risk assessment. To assist the Planning Team, surface and underground consult- ant engineers were appointed to prepare feasibility studies of specific civil and engineering problems.

Jan 1, 1979

By M. G. Ayat, B. C. Scott

H. P. Ferri I refer to the article "Degradation Process in Coal Slurry Pipelines" by M.G. Ayat and B.C. Scott in the September 1988 issue of Mining Engineering. I would like to congratulate Dr. Ayat and his colleague on a very interesting and valuable piece of work. This article is an excellent one, describing a real phenomenon that has been ignored for so long. I do, however, have an objection. The article fails to address the degradation process when coal is processed or transported in other ways than slurry form, particularly those employed in this work. Could, for example, screening (wet or dry) have contributed to the extent of degradation? Perhaps scanning electron micrographs of the samples examined and after screening would have helped to clarify this. I would like to point out that degradation is also observed in pneumatic conveying systems, mechanical conveying, and other means of transportations employed by the mineral industry. Reply by M. G. Ayat We gratefully acknowledge Dr. Fern's comments on the subject paper. As he so rightly points out, the degradation process is a real problem, not only in coal slurry pipelines, but also in many handling and processing equipment employed by the coal and mineral industry. Scanning Electron Microscopic examination of samples may offer very little information about the extent of degradation for several reasons. One is that preparing a representative sample that has undergone degradation will be extremely difficult if not impossible. This problem is exacerbated by the fact that SEM requires only very small amounts of material for testing. Secondly, there is a sample preparation step involved in the SEM examination and, as such, it would be very difficult to associate the extent of degradation to either sample preparation or handling and processing operations. Finally, it is probably worth mentioning that degradation is a multi-faceted phenomenon involving many natural and man-made factors. The logical approach to this problem would, therefore, seem to be a "one-step-at-a-time" approach.

Jan 2, 1989

By D. -P. Georgescu

A native sulfur mineralization associated with pyrite and iron oxides containing 20% iron was quarried in Calimani Mountains, Oriental Carpathians. The wastes resulted from this exploitation activity, with a volume of 33 millions m3, were stored in four dumps while the wastes resulted from ore processing using flotation and the subsequent treatment were disposed of in a settlement pond. The investigations carried out in the entire mining area focused on the following two aspects: - the impact of environmental factors mainly on the hydrographic network; - the characterization all pollution sources, namely dumps, leachates and the quarry and the assessment of acidic drainage generation. The total sulfur content of the excavated ore was 3.8% while in dumps it ranged between 0.54 and 1.06%. Analysis of samples collected along the hydrographic network, draining the mining area, resulted in pH values ranging between 1.7 and 2.83 as well as high concentration of iron (4525 mg/L to 1.6 mg/L), copper (1.87 mg/L to 0.04 mg/L) and zinc (13.13 mg/L to 0.3 mg/L). Samples from the quarry, the dumps and the tailings pond were analyzed in order to deter-mine: - the maximum potential acidity (MPA); - the acid neutralization capacity (ANC); - the net acid production potential (NAPP).

Jan 1, 2005

By Johan K. Rodenburg

A major bauxite belt was discovered and evaluated from 1969 to 1974 by P. T. Alcoa Minerals of Indonesia in West Kalimantan, Indonesia. The proven reserves of beneficiated bauxite are 800 million tons averaging 38.6% AA1203 and 3.0% RSiO2. Inferred reserves of washed bauxite are in excess of 2 billion tons. The bauxite occurs as capping of low lying hills which were formed during the post Paleogene peneplaination stage. The overburden varies from 0.6 to 3.8 meters and the nodular bauxite horizon from 2.2 to 5.2 meters. The deposits were formed by the in situ weathering of predominantly acidic and basic intrusive rocks.

Jan 1, 1984

By Allen D. Graham

The coal industry in South Africa is briefly outlined. Test- work carried out on bulk samples of coal in the laboratory and used in the design of the Van Dyks Drift washery are described. Factors affecting the selection of equipment and the designed capacity of the plant are discussed. A description of the crushing plant, washery and load out section is given together with performance data obtained in the final acceptance tests. New features incorporated in the Van Dyks Drift plant and in more recent plants of the Group are outlined.

Jan 1, 1982

By F. C. Townsend

Centrifugal modeling was used to evaluate reclamation schemes of; (a) flocculants, (b) sand/clay mixes, (c) flocculants/sand addition and (d) capping with sand or sand/clay mix. Results suggest the hierarchy of effectiveness is: (d) capping, (b) s/c mixes, (c) flocculants/sand addition and (a) flocculants. Comparisions between currently used large strain consolidation computer programs reveal no difference between piecewise linear or finite strain calculations. Correlations between numerical and centrifugal model predictions reveal excellent agreement on magnitudes; however, rate predictions require improvement in laboratory input data and centrifugal scaling relationships.

Jan 1, 1987

By William G. Doepken

GENERAL DESCRIPTION The Henderson mine utilizes a highly mechanized, continuous panel-caving system to extract ore from a deep, massive, molybdenum deposit. The mine site, lo¬cated 80.5 km (50 miles) west of Denver, is situated at 3170 m (10,400 ft) above sea level in a steep valley on the eastern side of the Continental Divide. The mill site, located on the western side of the divide, is linked to the mine via a 15.5-km (9.6-mile) railroad tunnel. Mine production is scheduled to reach 27 215 t/ d (30,000 stpd) from the uppermost production level. This pro¬duction rate will have been reached within the four years following an intensive ten-year preproduction development program. A second production level, due to come on stream in later years, will expand production capabilities to 31 751 t/d (35,000 stpd). The mine, which employs approximately 2000, has blocked-out ore reserves of 220 Mt (242 million st) at an average grade of 0.42% MoS2. Geology The Henderson deposit is composed of two partially overlapping ore bodies that lie 1080 m (3600 ft) beneath the peak of Red Mountain. The ore bodies are entirely within a Tertiary rhyolite porphyry intrusive complex that has intruded Precambrian granite. The de¬posit is elliptical in plan with overall dimensions of 670 x 910 m (2200 x 3000 ft). In section it is arcuate with an average thickness of 185 m (600 ft). The top of the deposit is at an elevation of 2610 m (8700 ft) while the lower limits range from 2340 m (7800 ft) on the west to below 2100 m (7000 ft) on the east. The mineralization is relatively continuous in the ore bodies and consists of molybdenite and quartz in random to subrandom, intersecting, closely spaced veinlets. Cavability RQD (rock quality designation) * values measured from Henderson drill core and compared with the RQD values from the Climax and Urad block-cave mines in¬dicated that the Henderson ore would cave but with difficulty and that a high percentage of the cave ma¬terial would be blocky. Initial caving experience shows the Henderson ore caves easier and with greater frag¬mentation than was indicated by the RQD values. Pos¬sible reasons for this are: 1) The greater lithostatic load at the Henderson has a greater effect on caving and fragmentation than anticipated. 2) The relief of confining pressure due to caving action and brittleness of the rock is enhancing breakage. Mine Layout The Henderson mine layout was designed from its inception for a large-scale, rubber-tired, continuous panel-caving mining system. The ore body is vertically divided into three major mine levels (Fig. 1). The top¬most level (8100 level), which is 2469 m (8100 ft) above sea level, is the current mine production level. The intermediate or 7700 level, which is in the initial

Jan 1, 1982

The Bureau of Mines, U.S. Department of Interior, is currently investigating strata interactions associated with the mining of multiple coalbeds. Strata interactions due to subsidence are a result of undermining. This study involves underground investigations at a mine where room and pillar panels are actively being developed through an area of the Sewickley Coalbed which was subsided by undermining of the Pittsburgh Coalbed. Research to date indicates that undermining had little effect on upper mine pillar stability, but had a more severe effect on the development and maintenance of entries. Roof-to-floor measurements recorded over four times more convergence in entries developed over gob as compared with entries developed over support pillars in the lower mine. Consequently, this has led to major roof falls in the active panels, resulting in considerable production delays and supplemental roof support costs.

Jan 1, 1985

By R. A. Cummings

From before the turn of the century until as recently as the 1950s, relatively shallow coal reserves near the margins of the Illinois Basin were extracted by room- and pillar methods. Subsequent development has, in many cases, extended onto ground with high subsidence potential. The same state of affairs exists in many other historical coal mining districts, as well as in Illinois. Pit subsidence in Illinois is particularly common in the towns of Streator, Carterville, and Herrin, although there are others. Pit subsidence is characterized by distinct circular or oval depressions and normally is associated with shallow mining and thick soil relative to the thickness of rock.

Jan 1, 1985

By J. H. Jennekens

INTRODUCTION "Most people would probably agree that some degree of government control and regulation is essential in modern society, and it will likely continue as an important part of our social organization for the foreseeable future. But most of us tend to be ambivalent about it. In one situation or another we are likely to see government commitment to social benefit programs or regulatory devices either as an expanding encroachment on the freedom of the individual or as an undue interference with private enterprise or with the rules of the market place. But even where there is agreement as to the desirability of government initiatives, either in general or in a particular context, it by no means follows that there will be approval of the mechanisms or procedures used or the means of carrying them out." The above statement is taken from a 1980 Working Paper of the Law Reform Commission of Canada prepared in connection with its study of the exercise of administrative law in Canada and the practices and procedures of administrative tribunals. The Atomic Energy Control Board (AECB) is one such administrative tribunal, and as the federal nuclear regulatory authority, it is responsible for licensing the production, possession and use of nuclear materials, equipment and facilities and enforcing compliance with licence conditions governing the health, safety, security and environmental aspects of the activities involved. Although the AECB was established 35 years ago with the passage in August 1946 of the Atomic Energy Control Act, like many administrative tribunals its role and functions and the regulatory process which it applies have evolved significantly during this period. The changes which have taken place over the years reflect not only the vast scientific and technological developments which have occurred but also the marked differences between contemporary society and the social milieu of the mid-1940s. However, the basic philosophy of nuclear regulation in Canada and the underlying principles of the regulatory process have changed very little. Certainly, the process is far more open in terms of the general public, it has become appreciably more comprehensive and systematic in terms of the depth and extent of both the pre- and post-licensing technical evaluations which are conducted and the ensuing compliance program. Furthermore, it now applies to the whole of the nuclear fuel cycle as well as the industrial, agricultural and medical applications of radionuclides. Nevertheless the following fundamental principles remain unchanged: a. primary responsibility for achieving high standards of nuclear safety and environmental protection in the design, construction, commissioning and operation of nuclear facilities resides with the licensee; b. the credibility of the nuclear regulatory process depends not only upon its technical correctness and practicability, but also upon acceptance by the public-at-large of its perceived effectiveness and efficiency; c. regulatory criteria and principles should be concise, clearly stated and understandable; d. regulatory decision-making should be based upon stated criteria and principles taking into account pertinent scientific and technical facts only; e. fairness and impartiality must characterize all regulatory decision-making; f. the regulatory process should be subject to a comprehensive periodic review and evaluation to ensure that it continues to produce the desired results at justified costs. EXPLANATORY NOTES The mere statement of a set of principles is a relatively simple task. Far more difficult is the explanation of what these principles mean in practical terms. To stipulate that a licensee bears the primary responsibility for achieving and maintaining high standards of nuclear safety and environmental protection may be regarded by some as an attempt by the regulatory agency to evade the responsibilities assigned to it. However, this is not the case. It is unrealistic for anyone to claim that a licensee only complies with accepted norms of public and occupational health and safety and of environmental protection because of the fear of prosecution. The vast majority of citizens conduct their affairs in a proper manner not because there

Jan 1, 1981

By L. A. Roe

The year 1867 marks the first year of commercial production of phosphate rock in the United States. South Carolina produced almost all of the domestic output of mineral phosphate until phosphate mining began in Florida in 1888. During the period 1868 to 1949 the total marketed production of domestic phosphate rock was about 186 million long tons of which 71.5 percent was produced in Florida, 18 percent in Tennessee and 7 percent in South Carolina (1). From 1949 through 1960, Florida phosphate rock production has ranged Prom 71 to 77 percent of the total domestic production. Since three-fourths of the domestic phosphate production is from the Florida field, and since most of the phosphate from the Tennessee and Western fields is not processed, but used directly as electric furnace burden, this paper will concern itself almost entirely with water requirements for mining and processing ore from Florida. Figure 1 summarizes phosphate rock production for Florida vs. total United States production over the period 1947-1960.

Jan 1, 1962

By Andre C. Zingano

It is a very difficult task to estimate the immediate roof and support behavior in a room-and-pillar mining section in the initial phase of the mining project. There is little information available at this phase, and it is restricted to geomechanic characterization of the rock layers from cores samples, and the in-situ instrumentation of experimental entries and intersections. Even being a pilot excavation for roof support test a good indicator for the behavior of the immediate roof, its behavior for a full excavation mining section is different from a single intersection of two entries, mainly because the stress redistribution caused by the multiple entries excavation and face advance for a full excavation section. The objective of this paper was to calibrate a 3-D numerical model of an experimental intersection, based on the in-situ instrumentation of an experimental intersection excavation, and the geomechanic description of the rock layers. The numerical model was built with the same specifications as the excavation test, including the entry geometry and roof support. The numerical model calibration was based on wire extensometers that were installed at different positions in the roof of the pilot excavation, and on the geomechanic characterization of the rock layers that form the roof, coal seam, and floor. Therefore, it is possible to estimate whether the roof support specification adopted in the test phase will be good enough for the development of the entire mining section.

Jan 1, 2009

By J. E. Russell

The purpose of this paper is to describe an independent study which forecasts Texas coal production, specifically for electric power generation. This study, extending to the year 2000, is justified on the following basis. Texas produces and consumes considerably more electric energy than any other state, has consistently high growth rates in the population and industrial sectors, and has large lignite reserves. Also, since recent forecasts have been criticized as overly optimistic, this study is timely when considering the long lead times required in obtaining new power sources. In the study demand for electric energy was assumed to rest on two dominant factors: 1) overall state of the Texas economy as measured by the Texas Gross State Product (TGSP) and 2) Texas population. Demand models were prepared and tested following a study of several options. A final linear regression demand model with time lags for the two variables was chosen on the basis of good correlations. On the supply side, uncertainties such as impact of nuclear sources, gas-fired cogeneration, and ratio of imported to lignite coal exist. These uncertainties were studied with high and low cases for effects on lignite. Finally a simple supply model was chosen. Results of the study indicate that lignite production in Texas will rise from the current (1984) 40 million tons per year (XTPY) to the range of 77 to 124 MTPY and more probably 100 HTPY in the year 2000.

Jan 1, 1984

By Fathi Habashi

OXIDE ORES can be divided into two groups: 1) Simple oxides (Table 3.1). 2) Complex oxides. Those ores containing minerals composed of two oxides; an acid oxide (Cr2O3, Nb2O5, etc.), and a basic oxide (CaO, FeO, MnO), as shown in Table 3.2.

Jan 1, 1970

By Gene R. Block

The most economical method of reclaiming land that has been mined, whether it be in urban areas or in rural areas, is when the final configuration of the mining area is that which is required by the subsequent use. Surprisingly, there are a number of examples of this situation. In the arid southwest where water production for the expanding population is a problem, many urban sand & gravel excavation areas subsequently serve as holding basins for ground water recharge. In other areas of the county where water is not in short supply, sand and gravel excavations can be planned in such a way that subsequent land uses such as parks and homesites can be enhanced by utilizing the excavated areas as a water amenity. Reclaiming land for agriculture is another example of utilizing the excavated area for a subsequent use providing the excavated area has not been mined too deep. Other than replacing the layer of topsoil on the excavated area, the final configuration of the mining area is in many cases ready for the subsequent agricultural use.

Jan 1, 1984