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By H. K. Lin

Residual cyanide in cyanidation tailings can be detoxified by its oxidation to cyanate, as in the Inco and Degussa processes. However, cyanate, the product of detoxification and other oxidation processes, may be reduced to cyanide in reducing environments, e.g., deepwater discharge of cyanidation tailings. This study shows that the reduc-tion of cyanate to cyanide occurs and that the reduction rate increases with decreasing solution redox potential. Solutions with lower pH favor the reduction rate. No significant difference was observed between the results of tests prepared with distilled water and seawater, and the presence of cyanidation solid tailings does not show an effect on the reduction. Because cyanate can be reduced to toxic cyanide, causing environmental concerns, the deepwater discharges of cyanidation tailings must be handled carefully.

Jan 1, 2008

By L. Xu

Since the establishment of the standard dust concentration of 2 mg/m3, a strong effort has been made by mining engineers and researchers to provide better dust control equipment and procedures for underground coal mines. Particular areas of success have been control of dust generation by better coal-cutting strategy, better design of water sprays for dust suppression and air movement, use of scrubbers, and improved design of face ventilation systems. A drastic improvement occurred over time such that the average dust concentrations for continuous miner operators dropped from 6.5 mg/m3 in 1968 to 1.3 mg/m3 in 1980 and for auger, cutter, longwall, and roof bolter occupations from 2.7 mg/m3 in 1973 to 1.6 mg/m3 in 1980 (Niewiadomsky, 1983).

Jan 1, 1990

By A. Bergmann

Location The Meggen Mine and the concentrator plant of the "Sachtleben Bergbau G.m.b.H." are located in the southern part of the Ruhr-district of the Federal Republic of Germany. The mine has been in operation for more than 100 years, but the concentrator described in this paper was built in 1962 and started up in January 1963. Goelogy and Mining The Meggen ore-body is of sedimentary origin and occurs in a zone of limestones, graywacke and shales of Devonion age. The average thickness of the deposit is 3 meters and, due to an intense folding of the area, the mineralized zone dips very steeply at 800 toward the north. The ore consists of 85 percent of sulfides and 15 percent gangue that mainly contains silicates from the host rocks. The principal ore minerals are pyrite (67 percent), sphalerite (16 percent) and galena (2 percent) with minor amounts of marcasite and only traces of chalcopyrite. As shown in Fig. 1, the sphalerite and galena are very finely disseminated in the massive pyrite of the Meggen ore, and a very fine grinding combined with a special flotation technique are required to liberate the valuable sulfides and to produce separate concentrates of lead, zinc and pyrite. Mining is performed by the sub-level stoping method and employs trackless equipment. Present operations provide ore from the 600 meter level. Annual ore production is 870,000 metric tons.

Jan 1, 1972

By S. K. Ghosh

This paper discusses how the information on ash composition, ash-fusion temperatures, and ash-slag viscosity can be utilized to predict slagging and fouling potentials of a particular coal. A review of several empirical parameters which are commonly in use for determining such potentials is given. Also, some guideline values for interpreting the relative propensity of slagging and fouling of various types of coal are provided.

Jan 1, 1983

By Chulho C. Song, Liam Coleman

Alkaline pressure oxidation (POX) is an oxidative pre-treatment option that is commercially used for high-carbonate sulfidic gold ores. The high carbonate grades within the feed ore shifts the ideal operating pH to a basic regime. Compared with acidic POX, alkaline POX typically requires additional steam input due to a lower sulfur oxidation load and a high rate of in-situ carbon dioxide generation that needs to be vented along with steam. The cost of this steam addition is the largest differentiator between acid POX operation and alkaline POX from a cost comparison. However, alkaline POX can offset these costs through reduced acid usage for pre-acidulation and decreased alkali reagent consumption for subsequent neutralization. This paper reviews the specific operating cost impacts of acid/base consumption between alkaline and acidic POX with ores which require pre-acidulation, the overall economics of alkaline POX, and the regimes in which alkaline POX is economically favorable. The findings aim to guide industry professionals in making informed decisions for alkaline POX adoption by providing a summary view of its operational benefits and costs, contributing to the development of cost-effective and sustainable gold ore processing techniques.

Feb 1, 2025

By John Drew Ridge

Recent work by Haas has made available information on densities and vapor pressures of solutions of differing salinities at temperatures up to 330°C. From these data it is possible to predict the behavior of volcanic exhalations of various degrees of salinity as they approach the sea floor. Particular attention is devoted to solutions of 5.0 weight per cent NaCl and 20 weight per cent NaCl, two fluids that approximate quite closely the salinities of what Roedder termed: (1) normal hydrothermal fluids and (2) fluids typical of stratiform deposits of low-temperature conditions of origin. It is apparent that solutions above 220-230°C. cannot reach a sea floor on which the depth of water is 600 feet or less in the liquid state but will boil at some appreciable depth beneath the sea floor. Such boiling would result in the precipitation of all constituents of the ore fluids of significantly lower vapor pressure than water. The principal such constituent would be salt, and no sulfide deposits, the major constituent of which is salt are known. It follows, therefore, that ore fluids probably never get close to the sea floor of shallow seas at temperatures high enough to permit boiling. Ore fluids significantly above 230°C. can reach the sea floor in the fluid state only if the depth of the sea in the area. in question is well above 600 feet, for example, solutions at temperatures of ±300°C. reach the sea floor in the liquid state only if the depth of sea water is slightly over 3000 feet. Ore fluids reaching the sea floor at such depths may be the parents of such fluids as the Red and Salton Sea brines. On the basis of these data, the Cyprus and Kuroko deposits are discussed.

Jan 1, 1973

By Rodney K. Morrison

MARTA, The Metropolitan Atlanta Rapid Transit Authority, is building a 53 mile heavy rail transit system to serve the City of Atlanta. Phase A of the Rail System, consisting of approximately 14 miles of at-grade, aerial and subway construction is underway. Metropolitan Atlanta lies in the Piedmont Geologic province of Georgia and is underlain by rocks of essentially granitic and gneissic nature. The soils encountered are primarily silty sands which are in-place weathering products of the parent rock and exhibit their relic structure. In general, these materials have presented no unique construction problems other than those created-by proximity of manmade structures, local availability of ground water, and top of rock elevation. The subway sections of primary interest in this paper consist of hardrock and soft ground tunnels and extensive cut-and-cover sections. The cut-and-cover construction includes excavations as deep as 80 feet. Temporary support systems in these deep excavations consist of soldier pile-timber-lagging or soldier pile-tremie concrete (SPTC) walls with internal bracing or tiebacks. In shallow cut-and-cover sections, where right-of-way economics permitted, slopes were laid back partially or fully to reduce or eliminate the need for bracing systems. Dewatering systems were required in most open cut excavations. Due to the close proximity of utilities and existing structures to the MARTA

Jan 1, 1979

By C. S. Kucukkaragoz

An ilmenite concentrate was reduced in the solid state with carbon under argon atmosphere at temperatures between 1000oC and 1400oC. The ilmenite concentrate and 50% excess carbon were reacted to achieve the highest attainable degree of reduction at each temperature and the reaction products were subjected to a series of analytical work by optical microscopy, X-ray diffraction analysis and SEM ( EDS) analysis. The ilmenite remained unaltered at 1000oC and had a slight change in its composition at 1050oC. A secondary oxide phase containing metallic nuclei was detectable at 12% reduction at 1100oC. The reduction of TixOy took place in a sequence changing the y/x ratio from 2.0 to a value less than 1.0 at 84% reduction at 1400oC. Metallic phase consisted of Fe and C initially and started to include Ti at the later stages. Complete reduction of TixOy to metallic Ti was not possible at these temperatures.

Jan 1, 2005

By E. C. Robertson

D.G. Wilder I found the suggestion that the amount of displacement of a fault can be numerically related to the thickness of gouge or breccia to be both intuitively satisfying and intriguing. I have long agreed that there is some type of relationship between the amount of gouge and the amount of displacement of faults. I congratulate the author for developing a numerical relationship between them. However, I am concerned that the limits for applying this relationship be fully understood. An underlying assumption in this approach is that there is either a uniform thickness of gouge or breccia along a given fault or the thickness does not vary widely. Since it is not always possible to confirm this, the displacements derived by this method should be viewed with caution unless significant fault extent can be observed. At the Nevada Test Site, in drifts constructed in granite for test emplacement of spent nuclear reactor fuel, we found a fault with 0.3 to 0.4 m (12 to 16 in.) of clay gouge. Within a few meters of this location, the fault had no clay gouge, but rather consisted of a highly fractured zone with significantly altered rock and some slickensides. Based on Fig. 1, the 0.3 to 0.4 m (12 to 16 in.) thickness of gouge would indicate a displacement in excess of 30 m (98 ft). However, no gouge thickness would indicate essentially no displacement. Based on a quartz vein that terminated on the fault, and is not identified nearby, an estimated displacement of more than a few meters was made. This estimate is consistent with that obtained using the regression line proposed in the paper if the 0.3 to 0.4 m (12 to 16 in.) thickness for the gouge is used. However, using the regression curves with zero thickness would not yield results consistent with what was observed in the field. Therefore, it is important to recognize that the suggested procedure would properly yield a range of probable displacements. ? *Work performed under the auspices of the US Department of Energy by the Lawrence Livermore National Laboratory under Contract W-7405-Eng-48. Reply by E.C. Robertson It is certainly true that the t (thickness) of gg-bx (gouge and breccia) on a fault does vary along the fault. My observations have been that near the termination of a fault, the displacement d is small and the t is also small, whereas the maximum d and t will usually be found in the central part of the fault. The information on gg-bx and t of the fault found in granite in the NTS tunnel by Mr. Wilder could be interpreted somewhat differently than he does. He speaks of the fault changing within a few meters from 0.3 to 0.4 m (12 to 16 in.) of clay gg to "a highly fractured zone with significantly altered rock and some slickensides," but no gg. The highly fractured rock may be taken to be bx, rock not so finely ground as gg but still crushed by the fault movement, equivalent to the gg in my usage, and probably occupying about the same t. Mr. Wilder's estimates for the fault in the NTS tunnel for t of 0.3 to 0.4 m (12 to 16 in.) and for d of a quartz vein, in excess of "a few meters," would place the point on the low side of the central trend line in my Fig. 1, at the lower limit. There is, of course, a problem with determining d using displacement of only one planar surface. It would be greater or lesser depending on the rake of the movement. Finally, estimating the d of a fault from its t should be made with awareness of our present uncertainties, as pointed out by Mr. Wilder. Although the central trend line in my Fig. 1 has a ratio of d/t of 100, I have put the limiting ratios at 10 and 1000. Understanding of the values of the ratio will be improved only with collection of more data, for which the discussion of Mr. Wilder is much appreciated. G.C. Waterman E.C. Robertson's paper provides significant information to a geologist attempting to deduce fault offset by noting the products of structural dislocation. However, considerable mapping in underground and open-pit mines, and examination of structures produced in different geological settings, have convinced me that gouge and breccia thickness are controlled by geological conditions and fault movement. The following paragraphs suggest geological variables that control them. 1. Depth of Loading A near-surface fault resulting from tensional stress has more breccia/gouge than is produced by a similar stress at considerable depth. A deep-loaded compressional stress may produce a linear zone of schist, or structural dislocation may occur along an earlier formed belt of schist. Such "shear zones" are common in Canadian mines in precambrian rocks. In neither case can offset be directly deduced by an analysis of the minimal gouge/breccia in the shistose rocks. At greater depth, stress may be partially to wholly relieved by flowage. I vividly recall first noting the regional "Midas Thrust" in the Lark mine, Bingham Mining District, UT (where we called the structure the North Fault). My recorded notes, as I remember them, showed a narrow gouge streak separated the `Jordan" and "Commercial" limestone units from impure, muddy limestone beds of uncertain stratigraphic position. The visible structure did not indicate the great importance of this premineral fault

Jan 12, 1984

By A. K. Majumder

Particle motion in fluids is a subject of considerable practical importance to engineers working in fields such as hydraulics, river mechanics, chemical engineering and mineral processing. Many mathematical models have been proposed to predict the terminal settling velocities of particles in a fluid medium. The selection of an appropriate mathematical model has, therefore, become a challenging task for practicing engineers. This paper reports on an attempt to identify some of the useful models found in the literature for predicting particle-settling velocities in a fluid under free- and hindered-settling conditions. From this study, it was concluded that there is no well-accepted model validated by experimental data available for predicting particle hindered-settling velocities in a suspension of polydisperse and polydens particles. Collective efforts should, therefore, be made towards developing a hindered-settling model, as this is an absolute prerequisite for many model structures in mineral processing and other engineering disciplines.

Jan 1, 2007

By M. K. Mohanty, H. Akbari, L. A. Ackah

Dry separation was the predominant method of coal cleaning in the United States from the 1930s to 1980s. The application peak of dry separators for cleaning raw coal was in 1965, when about 23.1 Mt of cleaned bituminous coal was produced. The main advantage of dry coal cleaning is the elimination RIWKH GHZDWHULQJ VWDJHV DQG VLJQL¿FDQWO\ UHGXFHG moisture in comparison to wet processing. In addition, developed dust control systems have made dry cleaning method an environmentally friendly process. The largest air-based coal cleaning plant was built in Pennsylvania in 1968 and could clean 1,272 t/h of raw coal sized smaller than 19 mm. This was followed by a decline in dry coal cleaning to less than 3.6 Mt in 1988. Some of the main reasons that shifted coal operations IURPGU\WRZHWSURFHVVLQJZHUHWKHQHHGIRUPRUHHI¿FLHQW separations with lower density cuts, increase in raw coal surIDFHPRLVWXUHVSHFL¿FDOO\LQXQGHUJURXQGPLQLQJWRFRQWURO GXVW ¿QHUSDUWLFOHVL]HUHTXLUHPHQWV LQFUHDVHLQ¿QHVLQUDZ coal from underground mines, and health and safety concerns related to dust and noise (Arnold, Hervol and Leonard III, 1991; Miller, 2011).

By L. G. Stolarczyk, Y. Luo, S. S. Peng

Detection and assessment of severe geological anomalies ahead of a longwall face greatly benefits the mining operation. Electromagnetic-based Radio Imaging Method (RIM) is one of the most promising geophysical methods for this task. Based on two decades of development, the latest RIM instrumentation (RIM-IV) has expanded its operational range up to 1,800ft.A site demonstration of the RIM-IV technology was recently conducted within a longwall panel. An extensive ground truth study was performed to evaluate the accuracy of the RIM survey results. This study compared the generated RIM tomograms of attenuation rate with the mapped geological anomalies. Three different approaches have been employed to examine the accuracy of the RIM results and to correlate the measured signal attenuation rates with physical properties of the coal seam. The study shows that the RIM-IV technology is able to identify and delineate those geological features that would severely affect the longwall mining operation.

Jan 1, 2004

By P. C. Thakur

In Part I of this paper, it was established that the width of longwall faces in highly gassy mines is primarily limited by the volume of air reaching the tail-end of the face. The ventilation air reaching the tail-end of the face should be not only enough to keep methane concentrations below the statutory limits (generally 1 percent) but also enough to prevent any gas layering. The air volume leaking from the longwall face into the gob should also be able to push the explosive methane-air mixture away from the gob area immediately behind the longwall face where active roof-fall is taking place (typically 30-45 m). The second group of variables that also controls the width of the longwall panel consists of (a) the rate of advance, (b) bleeder air quantities, (c) specific methane emissions for the gob area and, (d) efficiency and cost of gob gas capture. This paper will discuss the second group of variables and its impact on the optimum width of longwall faces in highly gassy coal mines.

Jan 1, 2009

By Steven I. Majtenyi

There is a growing interest among transportation planners to make more use of the subsurface to preserve the landscape and make transportation more efficient and economical. At the present time, utilization of the underground for transportation facilities is severely restrained by the adverse environmental impact and high construction costs. However, recent studies performed by the United States Department of Transportation indicate that, in spite of such problems, the volume of underground construction has significantly increased during recent years and projections point to continuation of these trends(1). It is estimated that the total volume of transportation tunnel construction will exceed $4 billion in this decade. This level of Investment justifies a significant research program. Due to the common interest in transportation tunnels and to the similarities of problems encountered during their construction, the tunneling research activities of the Federal Highway Administration (FHWA) are closely coordinated with the programs other agencies of the U. S. Department of Transportation DOT); specifically, the Federal Railroad Administration (PRA) and the Urban mass Transportation Administration (UMTA). The FHWA is responsive to the particular needs of these agencies but will benefit from the research results obtained also. In 1971, the Office of Secretary, DOT, initiated plans for an overall coordination of the DOT, FICA, UMTA, and FHWA tunneling research activities. The objectives of this effort have been to reduce tunneling costs by 30% and to increase the rate of excavation by 200% within 10 years. This coordinated program was developed and promoted during 1972 and 1973 by Dr. Eugene L. Foster, at that

Jan 1, 1974

By T. Cienski

The paper presents and discusses the results of a detailed study conducted on the subject of energy consumption in the comminution of industrial minerals. The study was based on pilot circuit testing, plant operating data collection, detailed equipment data and literature research. The areas covered by investigations include: high efficiency classification; air classifiers for cement grinding circuits; grinding aids in dry grinding: dry grinding circuit, control based on particle size measurement. Results obtained indicate a large potential for the reduction of energy consumption, in particular in the traditionally high cement clinker grinding circuits. Better classification techniques and correct application of grinding additives can significantly reduce power used per ton of product and also substantially increase grinding circuit output.

Jan 1, 1990

By M. Menéndez

Enhanced gravity separation appears to be one of the most promising methods for processing all types of <200-µm coal feeds and tailings. Systems based on this technology are reviewed, and the results of investigations based on C900 Multi-Gravity Separator tests conducted to assess the treatment of <200-µm, extremely difficult-to-wash coal settling pond tailings are presented. Multi-Gravity Separator processing tests of ultra-fine tailings with a high clay particle size content (22.6% <10 µm and 60.1% <40 µm) and a 69.56% ash content show that this material can be effectively treated after desliming (<10 µm) of clay-size particles to produce a coal with a 20.6% ash at a separator combustible material recovery of 69.3%. Desliming is shown to be critical in reducing coal ash content and combustible material recovery. Similar improvements are anticipated in the recovery and separation pro-cesses for other enhanced gravity separation systems from the desliming of feeds. Although not a conventional form of treating Multi-Gravity Separator data, the existence of well-defined polynomial relationships based on the product of drum shake amplitude and shake frequency relative to product coal recovery, product ash content and yields at varying wash water flows is demonstrated. Low-amplitude and intermediate- to high-frequency bed agitation are shown to produce optimum ash reduction results.

Jan 1, 2007

By Dan S. Nilsson

Small-scale mines are today expected to provide much of the increased production of metals, industnial minerals and coal this country demands in the future. But what is the size trend in the mining industry?

Jan 1, 1980

By Luttrell. G.

The profitability of coal mining operations is highly dependent on the performance of the coal blending and processing facilities. Many companies have recognized this fact and have instituted optimization programs that require large amounts of coal characterization data, extensive operational information and complex costing models. Unfortunately, this brute force approach to optimization is often overwhelming in terms of time and cost and is generally too inaccurate to be of value in day-to-day field operations. A simpler and more practical approach involves the use of ?micro-price? optimization throughout the coal supply chain. This fundamental concept assigns unit values to each type product (particle or groups of particles) passing through the production units. True optimization occurs whenever all particles with positive worth are recovered and passed to market, while all particles with negative worth are rejected. This paper describes the fundamental workings of the micro-price concept as applied to coal blending and processing operations. Several examples are also included to demonstrate the economic gains that can be realized via the application of this concept.

Feb 23, 2014

By Peter Klaver

Deep tunnels have been used for decades for the temporary storage of large volumes of urban runoff, both storm water and combined sewer overflow (CSO). Tunnels are attractive because they reduce surface disruption and do double duty as storage and conveyance systems, collecting overflows from multiple locations and transporting them for treatment to various facilities. Like any hydraulic system, however, there are dynamic effects that must be fully understood during the design phase so that the final constructed product does not have unintended negative consequences. Preliminary sizing of storage tunnels is typically based on the total volume required. For example, if studies have determined that a volume of 56.8 ML (15 million gal) will provide the intended level of control, then that figure can be used, along with a preliminary idea of the desired tunnel length, to compute the required diameter. Of course, filling a long tube with water from various points along the way is not at all the same as pouring water into a bucket, and these dynamic effects require additional attention from design engineers. The rapid filling of storage tunnels can lead to the formation of bores, which are essentially moving walls of water. An open channel bore can build in height until it reaches the crown of the tunnel, at which point it becomes a pipe-filling bore. Figure 1 depicts both kinds of bores moving upwards in a rapidly filling tunnel. Bores can strike the ends of tun-nels with tremendous force, driving water and entrained air upwards into dropshafts and creating strong pressure surges in portions of the tunnel that are already filled. If the hydraulic surges are high enough to reach grade, they can cause overflows and/or damage structures at the surface. Trapped air pockets can occur through several phenomena, including the reflection of bores off dropshaft structures and the occurrence of ?premature pressurization.? The latter refers to the situation where the inflow to a tunnel is increasing more rapidly than the tunnel can convey it, such that the pipe becomes surcharged at an upstream point while points downstream are still flowing as an open channel. These air pockets are a great nuisance as they migrate toward points in the tunnel where they can rise to the surface, which are often shafts that are already filled with water (Fig. 2). The ?geyersing? that results can be hazardous and costly.

Jan 3, 2010

By M. Pérez-Tello

A mathematical model to represent the expansion and fragmentation of copper matte particles oxidized under flash converting conditions is presented. The model assumes that the particles are initially nonporous, have a constant mass prior to fragmentation and travel at a constant velocity throughout the reaction chamber. The model requires the specification of the following five parameters: the particle expansion rate, a fragmentation diameter factor, a fragmentation size distribution parameter and the fractions of the finest and the coarsest particles in the feed that undergo fragmentation. The model predictions show good agreement with the experimental data collected in a laboratory furnace over a wide range of experimental conditions. The evolution of the size distribution of the particles along the reactor length was computed, and the model parameters were correlated with the experimental operating variables. Model predictions indicate that particle residence time is an important factor in the generation of dust. The presence of two maxima in the particle density function may be attributed to turbulent conditions prevailing in the furnace, which cause particles to follow different trajectories within the furnace even if they are injected at the same location.

Jan 1, 2008