Search Documents

By Ioannis Nicolaou

This paper demonstrates the method of approach for the optimization of such filters. This does not only incorporate the proven and simple recently developed equations for the calculation of the solids throughput, the residual moisture and gas throughput, but also introduces equations for the calculation of the specific product costs for both vacuum and hyperbaric filtration under consideration of the influences exerted by the filter compressor and a possible thermal drying. An easy-to-use method is offered which incorporates a special graphic representation concerning the plotting of the target parameters in dependence of the pressure difference with which the optimal process pressure difference can be established, independent of the specific cake permeability or product fineness. Finally, the optimization method is exemplarily demonstrated for a concrete application.

Jan 1, 1995

By H. Beecher (Original by) Charmbury

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

Jan 1, 1981

By D. Hodouin

The optimisation of mineral processing plants requires the evaluation of performance indices such as production rate, product quality, valuable mineral recovery and process efficiency. Decision to change operating conditions or equipment to improve plant performances rely on the significancy of the estimated performance indices. The better is the quality of the estimation, the better is the discrimination capability of the index and as a consequence the larger is the operation improvement. The reliability of performance calculation depends on the sensors nature, accuracy and location, on the data redundancy, on the correction method applied to raw data and finally on the propagation of measurement errors along the calculation of performance indices. To maximize the quality of the data collected for performance evaluation, the following techniques are presented, discussed and illustrated: redundancy and observability analysis, data filtering for mass conservation, variance analysis of performance calculation, and data acquisition strategy design.

Jan 1, 1991

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

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

Jan 1, 1992

By S. P. Mehrotra, P. C. Kapur

A phase-species classification is suggested for the mathematical models of flotation kinetics. Important models are discussed and the structure of their rate constants and parameters is analyzed. Split or enhancement factors are formulated for different kinetic models. The steady state dynamics of the flotation circuits can always be described in terms of these factors. For simulation of circuits, feed is characterized in a formal manner starting from a multivariate distribution of particles in flotation rate, size and mineral content. Synthesis of optimum circuits which simultaneously searches for the best process variables and structural parameters from a generalized master network is described. Trends in the areas of search algorithms, role of middlings and feed identification etc. are indicated.

Jan 1, 1989

By C. G. Anderson

In some parts of the world, silver chloride occurs naturally in deposits of cerargyrite (1) (i.e. horn silver). In other cases, silver chloride is produced and exploited for its well- known photographic or electrochemical properties. In this case, it is a valuable commodity needing no further refinement. However, silver chloride is frequently encountered in precious metals refining. In most cases, it is a by-product that occurs in small amounts. For example, it is a common occurrence in gold refining when using the Miller and Wohlwill refining processes or when parting fire assay beads. As such, the mode of reduction to elemental silver is of little impact on the overall refining economics. Thus, a variety of reduction methods are employed all enjoying varying degrees of popularity (2). On the other hand, silver chloride serves as a key intermediate in the production of fine silver by nitrogen species catalyzed acid pressure leaching of refractory silver concentrates. This has most recently been practiced at the Sunshine Mining & Refining plant located in Kellogg, Idaho. Thus, efficient methods of reduction, precipitation and materials handling on an industrial scale are of the utmost importance. In this presentation, the evolution of these methods will be detailed.

Jan 1, 1997

By S. Monette, D. B. Dreisinger, D. Vleeschhouwer, G. B. Harris, G. A. Kordosky

A new process for the recovery of pure (>99.95%) palladium and platinum is described. The process, which has been tested at the pilot scale, comprises (i) the simultaneous solvent extraction of palladium and platinum by a new Schering Berlin reagent, TN 1911, (ii) washing of the loaded extractant to remove co- extracted impurities, and (iii) differential stripping of first platinum at pH 3, and secondly palladium with strong hydrochloric acid, and (iv) precipitation of palladium and platinum salts, followed by reduction to metal. The process is, unusually, a non-ammonia one requiring only small amounts of ammonia at the end where final purification may be necessary for particularly complex feed solutions.

Jan 1, 1993

By Pasi Latva-Pukkila

Underground rock drilling has gone through intense development during the last 25 years. Mechanization and hydraulics have greatly increased the efficiency of drilling and improved the environment of the drill operator. As the total economy has become more and more important, the development has resulted in greater overall economy in drilling. The latest evolution step is computerization of drilling equipment. Computerization has been applied to tunnelling jumbos, long- hole drilling rigs and bolting rigs. With today's technology computerization is the natural way to increase capacity and productivity of the drilling process. However, it is still impractical to implement total "robotic" drilling. In computerized drilling the operator's role continues to be vital in controlling the drilling process and in analyzing the effect of individual parameters on the whole excavation process. Today this is called "CAD" - Computer Aided Drilling.

Jan 1, 1989

By A. Arik

1his paper presents a modified ordinary kriging technique referred to as the "Nearest Neighbor Kriging" (NNK). The method is a simple and practical tool to use when the ordinary kriging (OK) results are unreasonably smooth, especially when estimating recoverable ore reserves for deposits with skewed grade distributions. NNK is robust and globally unbiased like OK. However, it is more advantageous over OK because it can control some of the smoothing and conditional bias which have been the major pitfalls of OK in many grade estimation cases. The paper details the methodology of NNK and its application to a gold deposit.

Jan 1, 1998

By David Sugden

Intense, tropical weathering of Cretaceous-Tertiary sediments has developed similar laterites in distant areas of the Amazon Basin. In two areas, Trombetas and Paragomina s, bauxites of commercial potential arc found. The bauxite comes mostly from the lower horizon of the three component laterite. The laterite is overlain by a clay cover, possibly an integral part of the weathered profile. The laterites are found on almost flat plateaus with individual areas of up to 80km2. There is a close relationship between the morphology and the ldterites. The process of lateritization is allegedly Pliocence but probably continues today.

Jan 1, 1984

By E. Peuraniemi, S. Strömberg, S. Jyrkönen, A. Jokilaakso

Several sulfidic raw materials have been flash oxidized in a laboratory furnace in oxidizing atmospheres at temperatures of 500-1100°C. Chemical analysis was used to determine the oxidation degree, and optical and scanning electron microscopy combined with energy dispersive analysis were used for characterization of the reacted particles. The studied materials included both Cu and Ni concentrates and mattes. In fixed conditions, the temperature dependence of sulphur removal rate was found to be equal for all the copper concentrates studied. Nickel concentrates and Cu- and Ni-mattes were, however, found to be less reactive. Most of the particles were found to spheroidize and to fragment to small droplets under intensively oxidizing conditions. The product particles were frequently found to be iron oxide cenospheres or dense spheres with a composition of mixed Cu-(Ni-)Fe oxides.

Jan 1, 1998

By Wayne A. Ericson, Kirk S. Davis, Cornelis Winkler

BCI has developed a chemical process known as Ecophos® for the multi-industrial Pine Level Project in DeSoto County, Florida. Approximately 85 percent of the phosphogypsum at Pine Level will be converted to a very clean gypsum. The remaining 15 percent, including impurities plus some quartz tailings sand, constitutes what is termed redigestion solids. BCI has developed an alternative to the practice of disposing phosphogypsum in large above-ground impoundments. The proposed disposal method consists of mixing the redigestion solids with clays and reacting the mixture (leached tailings) with lime prior to disposal into the mine excavations as a reclamation soil material. Leachate water quality testing using lysimeter equipment indicates that the pore water associated with neutralized leached tailings meets maximum contaminant levels set for the drinking water standards of radium and selected primary metals.

Jan 1, 1992

By Nobuharu Isago, Atsushi Kusaka, Kosuke Kawata

"Rock tunnels suffered severe damage from recent large earthquakes in Japan, despite the empirical knowledge that tunnels tolerate earthquakes better than surface structures. Seismic design for rock tunnels have therefore become a fascinating subject for many tunnel engineers. However, even basic behavior, including deformation mode and loading magnitude for hard-rock TBM tunnels and conventional ones during earthquake, has not been fully understood due to lack of actual seismic data; while EPB and slurry TBM tunnels take account of seismic design in Japan if needed. This study conducted a dynamic measurement in an actual road tunnel constructed in rock. The strongest aftershock of “the 2011 off the Pacific coast of Tohoku Earthquake” (Mw = 7.1) occurred during the measurement, providing precious data to examine deformation mode of the tunnel. Considering the acquired data, numerical analysis was also performed to calculate loading magnitude to cause fatal fracture of tunnel lining during earthquake.INTRODUCTIONLarge earthquakes can pose serious risks even for rock tunnels, as evidenced by large earthquakes in the past. In the large earthquake in Japan in 2004 (Mw = 6.6), some tunnels suffered severe damage including collapse of their permanent lining (Mashimo 2005), even though the tunnels were constructed in ordinary ground conditions except for fault, fracture zone, portal area, etc. To mitigate such risks, mechanical behavior of tunnel lining during earthquake should be clarified; however, even basic mechanical behavior including load-bearing capacity of the tunnel lining against earthquake is not fully understood.Numerous damage modes were actually observed due to various ground conditions (eg. Wang et al. 2001; Mashimo 2005). Among them, major tunnel damage caused by earthquakes can be grouped into three main modes as shown in Figure 1, excluding extremely unusual conditions such as a tunnel located on a stratum boundary where the stratum stiffness varies significantly. TYPE-I shows flexural failure or crack by bending moment at shoulders; TYPE-II indicates compression failure or flexural compression failure at crown; and TYPE-III illustrates compression failure at sidewall, mainly observed on tunnel that was constructed using steel ribs and lagging method. These damage modes, Type-I, II and III, are predominantly caused by shearing, horizontal compressing and vertical compressing deformations of the surrounding ground, respectively (Kusaka et al. 2011; Asakura et al. 2001)."

Jan 1, 2016

By Keith G. Wallace, Malcolm J. McPherson

In order to model accurately a mine ventilation system in an existing mine, it is necessary to determine the resistance to airflow in all main airways. This is accomplished by measuring the airflow and pressure differential in each airway. Gauge and tube methods have been used to determine pressure drops in ramps and level airways. However, it has rarely been used in evaluating the frictional pressure drop in shafts. Because shafts commonly have the highest pressure loss in mines, it is critical that the resistance of these airways be determined accurately. This paper describes the theory and practice of using the gauge and tube method for determining the pressure drop in shafts. The pros and cons of using this method are discussed as well as a comparison between the gauge and tube and barometer measurement techniques. Case studies showing the accuracy of shaft gauge and tube measurements are also presented.

Jan 1, 1991

By Michael J. Shulman

During-all phases of exploration limited resources must be allocated among exploration methods and among exploration prospects. This problem,, an exercise in optimization, can be treated mathematically. For three objective functions - maximizing return, return to cost and return minus weighted cost - theoretical results exist which enable the exploration planner not only to gain valuable insight into the problem, but also to estimate the resources necessary and to allocate these resources for' at least-two stages of exploration prior to initial field work. A two-stage exploration strategy for volcanogenic-sedimentary iron in northern Egypt illustrates, how the results can be used. Stage 1 consists of an aeromagnetic survey to map the structure of five areas;" stage 2 consists of field reconnaissance work. For the three objectives, lower bounds are calculated as a function of exploration expenditures for each stage in order to facilitate the choice of an-optimal exploration budget. Nomograms are then presented which, based on the Kuhn-Tucker Conditions', enable the incremental allocation of airborne and reconnaissance effort among the five areas.

Jan 1, 1989

By Y. J. Wang

A subsystem-based approach to the characteristic curves for a multiple fan ventilation system is presented. The ventilation variables and their relationships associated with a fan branch are considered as a subsystem of the multiple fan system. For each subsystem, the solution curve is generated by replacing the fan with a hypothetical pressure source or, alternatively, by adding a hypothetical pressure source without removing the fan. The projection of the solution curve onto the coordinate planes results in two classes of subsystem characteristic curves: pressure-vs.-quantity and quantity-vs.-quantity. The subsystem characteristic curves are described and illustrated through example ventilation systems. These curves are also discussed using the network equations of a general multiple-fan system.

Jan 1, 1993

By E. De Souza, H. Heidrich

In underground operations the evaluation of blasting fume dilution times and the application of recirculation techniques require accurate determination of the concentration of toxic fumes produced by the explosive used. This paper describes a methodology for obtaining concentrations of detonation products from commercial explosives tested under typical rock confinement and looks into the development of techniques for reducing toxic gases produced by explosives. This paper also analyses the application of techniques for the removal of toxic gas which would enable reduced re-entry times, a reduction in the quantity of fresh air and the use of air recirculation techniques, thereby providing substantial economic benefits to the industry. INTRODUCTION Toxic fumes from blasting operations are among the most common and serious hazards encountered underground. The implication of high concentrations of toxic gases emitted from blasting on the mine ventilation system are very significant and, in many cases, catastrophic results have occurred. Because blasting is a routine practice underground, the mining engineer is always confronted with the problem of controlling the fumes within acceptable levels. Typical control procedures employed underground include preventing or reducing the amount of fumes liberated from blasting through the proper selection of explosives and proper blasting techniques; removing the fumes through local exhaust systems or auxiliary ventilation (dilution ventilation); blasting off-shift, or at restricted times; localizing or isolating the effects of blasting where workings are isolated or sectionalized in the ventilation system; and absorbing some of the components of the fumes using air-water sprays. Dilution is one of the most effective control measures against blasting fumes and is universally applied. However, for precise determination of the dilution times for the fumes to reach safe concentrations, accurate determination of the concentration of toxic fumes produced by the explosives used is required. Research work has been carried out in determining the types and volumes of gases produced from blasting. In the case of ideal detonations, the nature and quantity of the fumes produced can be predicted by thermo-hydrodynamic calculations. However, commercial explosives exhibit non-ideal behaviour which is enhanced by the relatively small diameters of application in underground mines. The confinement offered by the surrounding rock further complicates the situation. It is well recognized that confinement affects performance and consequently fume generation. A detailed data base of fumes generated by commercial explosives at various conditions is introduced and the effect of blasting parameters such as, confinement, shock desensitization and incomplete detonations on toxic fume production is described for a variety of commercial explosives in use today. Thermodynamic predictions on fume production by the explosive compositions tested are also presented and compared with experimental results and their significance in assessing the quantity of fumes produced is discussed. A mathematical model capable of determining dilution ventilation requirements and dilution times to reduce the fume concentrations in the blasting zone to acceptable levels has been developed and it is being incorporated into a network system so that the effects of blasting can be simulated in typical mine ventilation systems. Solutions to the problem of controlling blast fumes within acceptable levels are described. These solutions include the use of control procedures which prevent and reduce the amount of fumes liberated from blasting. The use of low fume explosives, proper blasting techniques, dilution ventilation and filtration can be combined to effectively control fume production and save on costs. The application of these techniques to enable recirculation of underground air with reduced quantities of fresh air requirements is evaluated in a case study.

Jan 1, 1993

Power consumption of stirred media mills has been studied by an approach developed from work on stirred reactors. Relationships between torque required to rotate both disc and pin impellers immersed in dense particulate media as a function of speed, impeller and tank dimensions, and other relevant variables are evaluated. Data collected during numerous different experimental conditions are analyzed. The results can be summarized and presented in the form of characteristic plots, general equations and dimensionless group correlations involving power and modified Reynolds numbers. Special attention is directed towards the rheological properties of the media, which is considered as non-Newtonian liquids and hence, the equation of power law liquids is employed. Procedure for estimating parameters of effective viscosity and scale-up guidelines with respect to power consumption are put forward.

Jan 1, 1994

In spite of our deep conviction that it would be wrong for the United States to enter World War II, when, after Pearl Harbor, we were actually in it, I felt that I must do all I could to help. The country had been so good to me that I could not decently stay on the sidelines. My first thought was that I might help with supply and administration in the Air Force, as in World War I. So on the evening of Pearl Harbor I wired the chief of our Air Force in Washington saying that I had been on Gen. William Mitchell's staff in World War I and was offering my services again. I received a noncommital answer, but after a couple of weeks was told to take my physical examination. I passed it, but nothing further happened. After helping to make plans for the wartime operations of Summit King and Desert Silver, Dorothy and I went to New York to spend Christmas with Molly and Peter, both of whom were in college in the East. I had to complete a report on the Argonaut mine in California first, though the war made my recommendations of dubious validity. Before Christmas I received wires from Temple Bridgeman, Phil Wilson, and other friends who had taken positions with government agencies responsible for securing mineral products needed for war use. They urged me to join them. It was evidently a case of not whether but how I could be most useful. After six uncertain days with the family in New York I took the night train to Washington on the 28th of December. I had a hectic day there. First I saw Arthur Bunker and Phil Wilson at what became the Aluminum and Magnesium Division of the War Production Board. Their office was in an old converted barracks. They asked me to examine magnesium deposits in Nevada at once, and then to look at other magnesium and aluminum properties. After leaving

Jan 1, 1976

By Fabio Amaya, Andrés Marulanda, Ramiro Gutiérrez, Alberto Marulanda

The behavior of a salt rock mass is strongly related to a creep phenomenon. The amount of creep depends on the level of stress generated in the underground excavation. Additionally, security conditions and the lifespan of an underground cavern excavated under this geological conditions depend on the evolution of creep. Based on the experience of the failure of the Old Underground Salt Cathedral of Zipaquirá(Colombia) and the construction of the new one, the theoretical framework to predict the creep behavior of a salt rock mass is explained. The theoretical formulations are calibrated based on actual observations of the material behavior to predict the lifespan of this striking structure.

Jan 1, 2003