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By Armstrong M

Two methods of Monte-Carlo simulations, one suggested by Matheron (1972) and the other by Rudenno (1983), have been tested for simulating coal deposits. To do this 2160 values of ash percentages were simulated using 60 known data points in a two dimensional grid, 20 m x 40 m. 1L is found that while both methods conserve the mean of the known distribution in the results of the simulations, only the first method reproduces the spatial covariance (i.e. the variogram), of the experimental data. The results show that for simulation of regionalized variables only the first method tested yields the desired results.

Jan 1, 1985

By K. C. Mills, R. Thackray

A test has been devised that can predict accurately the % crystallinity developed in a slag film formed between the steel strand and the mould. The % crystallinity in the test samples was determined and compared with that for slag films formed in the mould when casting with that flux. There was good agreement between the % crystallinity in the test samples and the slag films. It was found that additions of TiO2and ZrO2had little effect on the amount of crystalline phase formed, but additions of CaO caused a dramatic increase in the amount of crystalline phase formed. Various parameters (which can be calculated from chemical composition of the flux) have been plotted against % crystallinty in the test samples. It was found that the modified (NBO/T) ratio provided the best relation with % crystallinity for the various parameters tested. There commended relation is % crystallinity=141.1(NBO/T)-284.0. Keywords: continuous casting, mould flux, slag film, crystallinity, chemical composition

Jan 1, 2004

By R. Mariano

"The ability to optimise a concentrator from mill feed to final products requires a process simulator that integrates comminution, classification and separation stages. A key part of any such integrated process simulator is the inclusion of a model of mineral liberation in comminution to predict the particle composition distribution of the comminution products. This need was recognised by Gaudin (1939) who proposed a model of liberation based on the cubic fracture of a mineral texture composed of cubic grains of two minerals.This paper describes the development of a texture-based model of mineral liberation that builds on the method proposed by Gaudin. The approach described here, termed the JK-Gaudin Random Liberation model (JK-GRLM) uses as its basis the measured, volumetric mineral texture data that can be quantified for a given ore using X-ray micro-tomography. The textural data required as inputs for the JK-GRLM include the mineral grain size distribution. While the Gaudin model (in common with other existing liberation models) is a two-mineral (or two-phase) system, the JK-GRLM extends the approach to multimineral systems of up to 15 individual minerals, making it more widely applicable.An example of the application of the JK-GRLM to a base metal sulphide ore is provided. In the example the JK-GRLM is used to simulate the breakage of the measured ore texture and the particle composition distributions of the simulated progeny particles are compared to the measured particle composition distributions of ore that has been physically broken.The ability to calibrate this mineral liberation model with measured ore texture will allow it to be applied in greenfield situations where geometallurgical programs measure texture and in brownfield applications as a key part of integrated process simulations. The development of this model enhances our ability to simulate mineral processing operations as an integrated system."

Jan 1, 2016

By L. Tafaghodi, S. Sarbishei

"Following the depletion of nickel sulfide ores, laterites are considered as one of the main sources for producing nickel and cobalt. One of the primary steps in pyrometallurgical extraction of nickel from laterites involves partial reduction of the ore at temperatures below 1000°C. Studying the kinetics of laterite reduction provides valuable information on reducibility of nickel laterites using coal as a reductant. The present study investigates the reduction behavior of a nickel laterite by thermal gravimetric analysis and differential scanning calorimetry. Non-isothermal reduction tests and X-ray diffraction analysis were performed to find the main reactions that occur during the process. The kinetic parameters were calculated by Coats-Redfern method. The general model of simple reaction f(a)=(1-a)n was used for calculating kinetic parameters.INTRODUCTION Nickel (Ni) naturally occurs in the form of sulfide and laterite ores. Laterite ores are mainly available in tropical regions. Weathering phenomena during millions of years has led to the formation of several layers with specific mineralogy (Butt & Cluzel, 2013). The three main layers downward are limonite, smectite, and saprolite (Crundwell et al., 2011). Although laterites are the most available nickel ore resource (70%), their share in the overall Ni production is limited to 40% (Crundwell et al., 2011). The main reasons for not materializing the full potential of laterites are as follows (Ray et al., 1985): •,Laterite ores contain high water content (free and combined) which in turn results in high energy consumption of the extraction process. •,As Ni is present in the form of solid solution in laterites, physical upgrading methods such as flotation are not effective in increasing the Ni content before the extraction process. •,Extracting Ni from sulfide ores involve exothermic reactions which are beneficial due to decreasing the overall energy requirement of the process, however there is not efficient release of energy in the process of extracting Ni from laterite ores."

Jan 1, 2017

By K. Taniguchi, Y. Inada

When underground openings are excavated in rock mass for storage of Liquefied Natural Gas, hereinafter referred to as L.N.G., as its temperature is -162o C, steep temperature gradients and thermal stress occur around the openings. That is, the plastic zone and cracks around openings will expand with time. In this paper, the range of cracks which were obtained by the Crack Analysis Method and the range of the plastic zone which was obtained by the No Tension Analysis Method were investigated and compared.

Jan 1, 1986

By . M. Muskat

A THEORETICAL consideration of the mechanics of various water-flooding systems with the viewpoint of comparing their relative merits involves the study of two fundamental properties of such systems. On the one hand, it is important to determine the efficiency of the flood as measured by the percentage of the total area that is swept out by the encroaching water before water actually reaches the output wells. This is really a measure of the regional tendency of the water to "bypass" the oil. On the other hand, the various systems must be compared from the viewpoint of their resistances which determine the rate of fluid production obtainable for given pressures maintained at the water input wells. The first of these questions has been studied and very definite answers have been obtained by means of simple electrolytic models.1 These models showed that, in an ideal system, the percentages of the areas flooded out before water reaches the output wells are about 57 per cent for the direct line-drive flood (the input and output wells being equally spaced and placed in alternate parallel lines), 74 per cent for the regular five-spot network, and 79 per cent for the seven-spot network. With respect to the efficiency of the usual flooding arrangements, they are, therefore, given quite accurately by the above numbers. With regard to the resistances of the flooding networks, electrical conduction models have also been used successfully2 and are well adapted to the problem of determining experimentally the pressure distribution and streamlines, or over-all resistances of specific flooding networks. However, such models do not permit readily a study of the effect of changing dimensions or configuration within a network, since a new model must be made up for each set of dimensions considered.

Jan 1, 1933

By A. Hayatdavoudi, E. Apande

Introduction Troublesome shales have plagued the petroleum industry for more than 50 years. Unstable boreholes have been experienced when drilled into shale formations; sane have been studied almost at the beginning of rotary drilling. A little progress has been made since then, but much is still to be learned. No simple solution exists so far, but good drilling practices combined with good mud practices have been helpful. It is well known that shales in general have a strong affinity for water, and when water is adsorbed, the stability of the shale section of a well is reduced; cohesive strength will be re- bed, properties will be altered and shale will generally expand and/or crumble. The amount of water a shale will adsorb depends on the characteristics of its clay mineral and the ionic concentration of surrounding fluid. Fluid loss and the resulting hydration of an unstable formation can lead to serious downhole problems. The rate of fluid loss depends greatly on the permeability of the deposited cake. In impermeable formations, however, there is no loss of fluid into the formation. As such, shale, because of its very low porosity and almost no permeability, could be termed impermeable. Yet there is strong evidence that shale surfaces are wetted by an invasion of fluid into the formation through microfractures and jointed planes. It is this wetting that causes the shales to swell and slough into the hole, resulting in problems such as increased mud volume and treating costs, bridges and fill-up, stuck pipe, overgauge hole, poor cement jobs and increased cement requirements, and logging and completion difficulties. Drilling operations have been defeated by severe shale problems, resulting in & hole being plugged and abandoned after several weeks of drilling. Shales are we1l known as being difficult and costly to drill. Numerous fishing jobs have plagued drilling operations, and the cost of reaming tight holes ad weighting up the drilling mud to control shale sloughing has been high. The concept of controlling water loss to stop sloughing was introduced in the 1920's. It was known-then that calcium in fresh water re- strains clay £ran excessive swelling (theory of osmosis) . This reinforced the belief that calcium-based muds such as lime, gypsum and calcium chloride should minimize hydration of clays. Lime muds were then introduced for this purpose and others in the 1930-1940 decade1. They were used for shale inhibition but were not effective. In an attempt to improve them, a special calcium-type mud beam popular during the 1950's. Hole enlargement continued and they too were considered ineffective. During & early 1960qs, papers were published claiming that shale swelling could be prevented by using high concentrations of chemical thinner called Chrane Lignosulfonate1. This began the era of highly treated lignosulfote muds. Unfortunately, the hole enlargement problem continued. During & mid-1960’s, oil based muds were used for the purpose of inhibition of shales. Not until 1966 did Mondshine2 suggest that the water phase be saturated with calcium chloride. The cost of using oil based mud was considered by most operators not worth the additional hole stability. The potassium chloride-polymer muds were also used in many fields in the United States and western Canada. The use of these muds has been claimed to prevent clay swelling by inhibition and encapsulation in sane areas of western Canada. They are also expensive and their ueneral application is still experimental. To reduce filtrate loss when sloughing shale becomes a problem during drilling is a reasonable practice. This study will investigate the use of cationic organic additives to mud to form a protective barrier between the shale - which are primarily composed of clays - and water that will keep water from entering the microfractures and will also prevent them from hydrating. In so doing, an understanding of modern clay chemistry and & dispersive properties of cationic additives in water based systems will be our most valuable tools. This study will also present and solve a mathematical model for simulating cation transport phenomena in fractured shales using the Framdlich equilibrium adsorption isotherm. The studies will analyze wellbore failure and stability as affected by cationic organic material.

Jan 1, 1986

By M. E. Karabin, R. J. O'Malley

"A mathematical model of the roll casting process has been developed which predicts macro-variables, such as roll separating force, roll torque, and strip exit speed for a range of roll speeds. Continuum variables, such as interface pressure, interface shear stress, freeze-front shape, and internal temperature distribution are also predicted.The model consists of two independent segments: solidification and rolling. The solidification model is two-dimensional (thickness and rolling direction) and is capable of handling alloy solidification. The solidification model is employed until solidification through the thickness is complete, then the rolling solution is activated.The rolling model is a one-dimensional (rolling direction) mechanical solution based on the von Karman approach, coupled with a two-dimensional thermal solution. The flow stress is expressed as a function of the average through-thickness temperature of the strip.Experiments were performed using a laboratory roll caster to test and refine the model. Experimental strip exit temperatures were used as input to the model. Experimental and predicted roll torque and strip exit speea were forced into agreement at a single reference roll speed to obtain values for the coefficient of friction and the interfacial heat transfer coefficient. Using these values, good agreement was obtained between predicted and experimental torque and strip exit speed over the entire range of roll speeds examined."

Jan 1, 1986

By Dai Wang

Stoppings are necessary ventilation control devices for effective air distribution underground. However, one of the major problems underground mining has is that every stopping is a potential leaking source. Since air always flows from a point of high pressure to one of lower pressure, and the total pressure at every point in intake airways is higher than that in the return airways, air will always tend to leak from intake to return (Tien, 1996). In many mines, less than half of the air entering the mine actually gets to the working areas; the rest of it simply short-circuits directly to return airways through leaky stoppings instead (Timko and Thimons, 1983). Leakage through a stopping occurs because of pressure drops across the stopping and available leaky path in stoppings. Empirical equation has been widely used to characterize the relation the amount of leakage and variables that affect leakage. However the use of this equation requires accurate information for constants which are not always readily available. It is the attempt of this paper to derive an equation similar to the Atkinson Equation that can readily be applied to characterize pressure-leakage relationship for any given stopping.

Jan 1, 1998

By K. W. Edwards

The formulation of a theoretical basis for the evaluation of in-situ coal through the use of geophysical logs is outlined. This involved the development of an approach to the interpretation of resistivity in environments having multiple conductive and non-conductive components. Utilizing this approach and other conventional interpretation techniques, a program was developed yielding accurate determinations of the in-situ percentages of coal, water and ash for the evaluation of coal deposits. Basic information obtained from the CWA program can be utilized in numerous aspects of total mine planning . Some examples of the practical application of this method are included.

Jan 1, 1978

By H. F. Niemand, C. J. Postma, P. L. Crouse

"SynopsisThe separation of zirconium and hafnium is essential in the nuclear industry, since zirconium alloys for this application require hafnium concentrations of less than 100 ppm. The separation is, however, very difficult due to the numerous similarities in the chemical and physical properties of these two elements.Traditional methods for separation of zirconium and hafnium rely predominantly on wet chemical techniques, e.g. solvent extraction. In contrast to the traditional aqueous chloride systems, the AMI zirconium metal process developed by Necsa focuses on dry fluoride-based processes. Dry processes have the advantage of producing much less hazardous chemical waste.In the proposed AMI process, separation is effected by selective sublimation of the two tetrafluorides in an inert atmosphere under controlled conditions, and subsequent selective desublimation. Estimates are made for the sublimation rates of the two tetrafluorides based on the equilibrium vapour pressures. A sublimation model, based on the sublimation rates, was developed to determine if the concept of separation by sublimation and subsequent desublimation is theoretically possible.IntroductionZirconium requires several purification steps to conform to nuclear-grade specifications. Little information is available on the sublimation separation of Zr and Hf compounds, especially in the fluoride form, the majority of which deals with sublimation under vacuum conditions. On the industrial scale, only vacuum sublimation of ZrF4 has been reported. No records were found for the sublimation of ZrF4 in an inert atmosphere. Information on the sublimation rate of ZrF4 or HfF4 in an inert atmosphere is also limited. The rate is assumed to be dependent on several factors, of which temperature, area, and composition are considered the most important."

Jan 1, 2015

By Y Wang

Inadequate goaf gas control may lead to gas exceedances in the ventilation return air, which will trip power in longwalls and cause production stoppage. To effectively control gas emissions, Australian mines heavily rely on drilling vertical goaf holes to capture coalmine methane before it migrates to mine openings. The wide application of goaf gas drainage may change the goaf pressure distribution, lead to more ventilation air leakage, and consequently increase gas explosion and spontaneous combustion risks. This paper focuses on analysing goaf gas drainage production data from a case study longwall mine in Australia. The correlation between suction pressure, total flow rate, gas flow rate and air leakage rate were analysed in detail as the face-to-hole distance changes. Suction pressure is found to be positively correlated with total flow rate, and their correlation also varies at different goaf locations due to various goaf compaction and flow resistance. This paper also proposed a theoretical method to calculate the goaf resistance of ventilation air leakage pathways. Based on several basic assumptions and different goaf drainage scenarios, the leakage airflow pathway resistance in the goaf at different face-to-hole distances can be calculated. The model results suggested that the resistance of air leakage pathways from the working face to individual goaf holes increased with the face-to-hole distance. The resistance results can also be used to calculate the corresponding permeability at the same position, which can be used as input data for CFD or Ventsim models.

Oct 12, 2022

By C. J. Hall

An investigation of multi-shaft airflow problems by the author in 1976 (1) was presented in the hope of arousing considerable written comment, but in fact-. only one contribution (2) was forthcoming. The investigation in this paper is taken several stages fur¬ther, because the matter is of major importance in many American hard rock mines with complex networks extending over thousands of meters vertically. The examples used have all been generated thermodynamical¬ly and checked by motive column (denisty) calculations. Dry air has been used to reduce the amount of time spent on the rather complex calculations, but it has been shown (3) that the principals developed apply equally well to air/vapor/water mixtures. Initially the subject is investigated using both thermodynamic and motive column analyses. The latter part of the paper concentrates on a motive column presentation. Both methods are, of course, equally valid and give identical answers to any situation when correctly applied, as is shown in the worked examples.

Jan 1, 1980

By Bhattacharyya A. K

The current methods for predicting pillar strengths are reviewed. A two-dimensional model, based on the Mohr-Coulomb failure criterion, is proposed for determining the compressive strength across the width of a long pillar. The model can be used to determine pillar strength and the depth of the crushed (ie yielding) zone from the pillar edges. The values of the parameters in the model, namely the cohesion and internal friction angle of the coal seam, friction angles at the contact of the coal seam with the roof and floor are determined by matching the strengths predicted by this model with the Bieniawski pillar strength formula for pillar width to height ratios up to 5. It is found that the derived values of these parameters are quite close to the results from laboratory tests. Based on the model, a preliminary analysis of pillar stability is made.

Jan 1, 1995

By A. Fredriksson, R. Christiansson, I. Staub

A theoretical model based on DFN models and 2D DEM numerical modelling has been developed for evaluating the rock mass mechanical properties. The description of the methodology is non-site related and can be applied in any site for this type of characterisation. The methodology was developed in the frame of the Site Investigation programmes for a Deep Repository for spent fuel in Sweden, and validated on sets of data coming from the Äspö Hard Rock Laboratory. Un modèle théorique base sur des modèles probabilistiques de réseaux de fractures et sur un modèle numérique DEM 2D a été développé dans le but de déterminer les propriétés mécaniques de la masse rocheuse. La méthodologie développée peut être appliquée à tout type de site pour ce genre de caractérisation. Le modèle a été élaboré dans le cadre des programmes de recherche d’un site d’enfouissement des déchets nucléaires en Suède, et validé par une application au laboratoire de recherche souterrain à Äspö. Ausgehend von DFN-Modellen und 2D DEM numerischen Modellierungen wurde ein theoretisches Modell für die Auswertung von mechanischen Eigenschaften von Fels entwickelt. Die Methodikbeschreibung ist nicht standortspecifisch sondern kan überall für diesen Typ von Standordkarakteriserung angewendet werden. Die Methodik wurde in Schweden im Rahmen der Standortuntersuchungsprogramme für die Endlagerung von verbrauchten Brennelementen entwickelt und ist mit Hilfe von Daten des Äspö Hard Rock Laboratory validiert worden

Jan 1, 2003

By J. N. Hummel

THE methods of electrical prospecting, which employ contact electrodes to produce an electric field in the ground, furnish information concerning the constitution of the material beneath the surface, as indicated by the distortion of this artificially produced field and anomalies therein. To reveal the distortion of such field of known character, it is only necessary to measure qualitatively the direction of the field, using sensitive compensation methods. In such a case, the survey is relatively simple, and that is an important factor from a practical point of view, The distortion of the normal field thus determined permits an easy interpretation and gives approximate information as to the subsurface conditions, without the necessity of a thorough theoretical knowledge of the electrical field. The true field of application of the equipotential lines and search-coil methods, which are based on this principle of directional determination of the electrical field in the ground, is that of search for deposits of economic minerals for the mining industry, although they can also be used in solution of other problems; for example, in the determination of the strike of anisotropic beds. The distortion of the electric field as represented by the picture of equipotential lines or other measured curves is striking only when bodies having conductivities different from that of the country rock are embedded in the underground, or when the underground is anisotropic.

Jan 1, 1931

By M. Makarchian

Existing buildings sometimes experience excessive settlement under their design loads, or due to increased foundation loading, if a change of building use is required. One of the oldest and widely numerical study has been carried out of a simple idealised problem of an underpinned rigid circular foundation to better understand the behaviour of pile used for underpinning and load transfer mechanism from an existing foundation to the underpinning piles. The finite element method has been used for this analysis, with the soil treated as a two-phase elasto-plastic material. It is found that the effect of the length of the pile becomes more significant as pile length increases. As would be expected, the earlier the pile is installed, the less is the final settlement.

Jan 1, 1996

As a kind of collector, Xanthates are generally used to make sulfide minerals hydrophobic in flotation process. Xanthate adsorption on a galena surface has been widely studied experimentally. In this paper, DFT methods were employed to investigate the local adsorption interactions about the collectors,such as ethyl xanthate (CH3CH2OCS2?, EO) and ethyl trithiocarbonate (CH3CH2SCS2?, ES), absorbing on two different PbS clusters. From the results, it can be easily found that, on the edge or at the apex, both collectors, with two S atoms bidentate coordinating on the clusters, have surprising interaction energies, while on the surface, its interaction is relatively weak in the form of monodentate ligand. NBO analysis results reveal that there is at least a covalence bond with sulfur atom about 10% and lead atom about 90% when the absorbed lead is on the lattice edge or at apex, but, if the absorbed lead is on the lattice surface, no covalence band would be found. Meanwhile, the S-Pb bond, formed by the absorbed Xanthate and galena lattice, seems to have much more covalence characteristic than that formed in the PbS lattice inner. Furthermore, those data also imply that the difference of the collecting effect between the EO and the ES may be not notable, because of the similar distance and the interaction energy for the same interaction mode.

Jan 1, 2014

By A. E. Wells

IN 1866, Thomas Graham1 called attention to the volume of gases, three times the volume of the sample, evolved from a meteoric iron heated in an evacuated porcelain tube. From that time to this the occurrence and significance of gases in metals have been the subject of investigation by many workers, among whom Sieverts,2 Iwasé3 and 0. W. Ellis4 stand preeminent. Sieverts and Iwasé concerned themselves with the solubility of a number of gases in metals in the liquid and solid states. They determined the absorption coefficients of these gases, and in all cases found a sharp change in solubility at the melting point of the metals. Ellis analyzed the gases evolved by solidifying copper and those occluded by the solidified metal. Lobley and Jepson5 endeavored to determine the effects of hydrogen, carbon monoxide and nitrogen on the porosity of copper that was allowed to solidify in the presence of each gas after 30 min. exposure to it in the

Jan 1, 1930

By A. Baydusa, K. Barron

A theory for cutter roof failure in coal mines has been developed. It is shown that the key parameters influencing the likelihood of cutter roof failure are the rock strength, the vertical stress (depth) and the horizontal to vertical stress ratio. The support force necessary to prevent the development of this mode of failure is, in most cases, so high as to make it impractical to apply a force of such magnitude. It is, therefore, better to allow the failure to occur and to design a bolting system to support the dead weight load of the failed block. This is probably best achieved by using a yielding bolt system (such as split set bolts) which is anchored well beyond the top of the potential failure block. The maximum potential caving height determined from this theoretical approach compares favourably with field observations reported in the literature.

Jan 1, 1999