This study explores the impacts of physical and policy variables on the economics of the development of a hypothetical 500 t/d underground polymetallic (Zn-Ag-Pb) vein deposit in the Sud Lipez region of the Bolivian Altiplano. Because of recent changes in the legal system, it is more attractive, interesting and worthwhile to examine the effects of policy variables that reflect the implications of the new legal system. For this purpose, an holistic investment methodology defined as the Investment-Worth model is developed to evaluate the risks and rewards to capital investments. Results of the study confirm that even in risky environments development of mining activities remain primarily driven by the quality of the ore reserves and the market conditions for the commodities of interest. Under the most probable scenario, the deposit of interest would remain a viable investment opportunity at zinc ore grades greater than 9%. Furthermore, the model demonstrates that the investment worth of a project is not the same across firms in the industry. Attractiveness of a project varies with economic and risk-related characteristics of firms. Specifically, investment in the zinc-based polymetallic deposit in the Altiplano will be more attractive to firms of at least moderate size that possess the required technical knowledge and skills but are not currently involved in zinc production.

No description available.

The objective of this research project was to investigate the effect of microwave treatment on the conversion of pyrite in coal in order to enhance its magnetic properties and to aid subsequent desulphurisation by magnetic separation. Key areas of this investigation include:- a review of the fundamental theoretical aspects of heating in an applied microwave field, a detailed literature survey of the potential applications of microwave heating to aid coal desulphurisation, a study of the transformation mechanisms of pyrite by microwave and conventional heating methods, a comprehensive review of the influence of heterogeneity on the dielectric properties of coals and the effect of high power microwave heating on the decomposition of pyrite in a high sulphur coal. A detailed survey of the literature has shown that although a significant amount of work has been reported on the microwave heating of coal, little information is available which examines the mechanism through which different coals heat in an applied microwave field. A study is therefore presented in this thesis which quantifies, for the first time, the structural ordering of carbon in a range of coals of various ranks and the relationship with their dielectric properties. The results show a clear relationship between the structural ordering of carbon in coal and dielectric loss factor. Essentially, as the structural ordering increases, the level of free charge (per unit volume) increases together with electron mobility which results in an increase in dielectric loss factor. The transformation of pyrite to form the more magnetic pyrrhotite and other related decomposition products by conventional radiant heating has been the focus of much research. However, little attention has been given to the effect of microwave heating on the mechanisms of pyrite transformation in inert and oxygen-containing atmospheres. The study presented in this thesis investigates the effect of temperature, particle size and heat treatment time to establish how these affect the transformation process and the subsequent nature of the final product. This study showed that exposure of pyrite to both conventional and microwave heating methods enhanced its magnetic properties as a result phase alterations at the particle surface. Conventionally heated pyrite samples showed the highest magnetic susceptibility increases, speculated to be due difficulties surrounding the temperature control and measurement of the microwave heated samples. From a review of the literature in this field of research and by SEM observations made for each sample test in this work a general pyrite transformation model as a result of microwave exposure is proposed. The effect of microwave radiation on the conversion of in-situ coal derived pyrite was also investigated. The study presented here extends previous work by others by assessing quantitatively the influence of higher applied microwave power levels on the conversion of pyrite in coal. Samples of run-of-mine high pyritic sulphur content (~12%wt) Kentucky coal were microwave pre-treated at varying exposure times using 8kW and 15kW of microwave power operating at a frequency of 2.45GHz. This work included initial material characterisation which consisted of TGA, optical microscopy and dielectric property measurement, followed by SEM/EDAX characterisation of both microwave treated and untreated sample specimens. This is the first time that microwave treated coal, embedded in a carnauba wax mounting medium, has been observed by this method with focus on the thermal alterations of the pyrite phase. It was demonstrated that with sufficient power and residence time, the conversion of pyrite to the more magnetic pyrrhotite is achievable using microwave irradiation. The amount of pyrrhotite formed as a result of microwave exposure varies with microwave residence time and forward power level. Comparisons of change in the iron sulphide species in the coal was made between microwave treated and untreated material. Using a multimode microwave cavity it was found that significant amounts of pyrrhotite were formed in 20s when using 15kW of microwave power. Treatment at lower power levels in this type of cavity was found to be less effective. The overall effect of treatment on the coal proximate character was minimal.

In order to ascertain whether kerogen and the heavy oil or bitumen generated during the initial stages of source rock maturation then go on to produce similar gas yields compared to the natural situation when they are present in source rocks, a study has been conducted on an immature type II Kimmeridge Clay Formation (KCF) source rock (Dorset, United Kingdom) with different total organic carbon contents (14, 25 and 30 % TOC), and all having an initial vitrinite reflectance (VR) of approx. 0.4 % Ro. Anhydrous and hydrous pyrolysis experiments were conducted on the whole immature source rock, the isolated partially matured bitumen-extracted source rock and the isolated bitumen (bitumen generated and extracted from the initial source rock) and mixtures of the isolated partially matured source rock and bitumen using two types of Hastalloy vessels (22 and 25 ml) at 320-420 °C for 7-48 h over a pressure range of 115-900 bar. Hydrocarbon gas yields and the increase in VR were greater from the whole rock experiments compared to the experiments on the isolated partially matured source rock and isolated bitumen (no mineral matter present), as well as the experiments on mixtures of the isolated partially matured isolated source rock and bitumen combined. The effect of particle size were also found to be of significance as higher gas yields were obtained from recombined mixture experiments using powdered samples (14 % TOC source rocks) compared to using rock chips (30 % TOC source rocks). Hydrocarbon gas yields, pyrobitumen yields, and VR values were found to decrease as pressure increases towards 500 and 900 bar compared to 180 bar at 350 °C where the effects of pressure retardation were found to be much more significant from the partially matured source rock maturation and bitumen in isolation than from the whole source rock. At 420 °C, gas generation, bitumen plus oil and coke yields were not affected by pressure, but VR decreases going from 310 bar to 500 and 900 bar. The results obtained demonstrate that the interplay of inherent mineral matter, reactant phase, source rock/kerogen, bitumen and pressure are key factors in determining the extent of hydrocarbon generation and source rock maturation in geological basins.

Recent research developments have suggested that microwave assisted comminution could provide a step change in ore processing. This is based on the fact that microwave-absorbent phases within a multi-mineral ore can be selectively heated by microwave energy hence inducing internal stresses that create fracture. A detailed review of existing literature revealed that little or no information is available which relates and examines the influence of hydrated minerals on microwave assisted fracture despite the fact that most important ores are associated with phyllosilicates, the vast majority of which are hydrated. A study was carried out on two Kimberlite diamond ores containing various types of hydrated minerals but devoid of any semiconducting minerals which are known to be good microwave heaters. The results confirmed that dehydration of minerals containing interlayer adsorbed water induces significant micro and macro fractures after microwave treatment. The significance of microwave induced fracture on beneficiation was investigated by conducting liberation and flotation tests on two porphyry copper ores. It was demonstrated that microwave pre-treatment improves beneficiation at sizes suitable for flotation and that higher improvements in degree of liberation are attained in coarser particle sizes between 212 and 425 µm. Flotation tests demonstrated a potential for real economic benefits in terms of value proposition. An increase of 8-10% in copper sulphides recovery from coarse sized particles (-400+200 µm) and an overall increase in grade/recovery of between 1-2% was obtained. The results also showed that microwave pre-treatment enhances selective mineral recovery as the grade-recovery of iron sulphides decreased in all but one microwave treated samples. The major drawback to further developments towards industrial scale application was found to be the lack of an effective continuous processing microwave applicator. Any future applicator designs must be able to ensure localised hot spots and confinement of all the microwave energy.

Self-oxidation and spontaneous combustion of coals is a problem of global concern. There are social, economic and environmental costs associated with this phenomenon and major incidents can, in extreme cases, lead to human casualties. More often however, damage is made to commercial facilities, the calorific value of the fuel is reduced and substantial release of noxious gases, particulate matter and CO2 may contribute to local and international pollution levels. This problem is not only restricted to coals, it also affects other carbonaceous materials such as biomass and potentially coal-biomass blends. A considerable amount of literature has been published, and whilst the causes are relatively well understood, the existing methods for predicting spontaneous combustion are not reliable enough for scientists or the coal industry. This research focuses on understanding the oxidation characteristics of coal, biomass and coal-biomass blends at low temperatures, with the aim of defining a set of experimental test procedures to identify coal and biomass propensity to spontaneously combust. Based on a comprehensive literature survey, two main research areas were identified as feasible sources of information to detect prone coals: microscopy and thermal analysis. Considering these, an extensive experimental program was carried out using 42 coals (including at least three well known samples prone to spontaneous combustion), 10 different biomass types, and a number of coal-biomass blends, including diverse particle and sample sizes, at different stages of the oxidation process. Initially, pulverized coal samples (size <106µm) were subjected to thermogravimetric and calorimetric tests (small sample size), and differential thermal analysis (large sample size) using a large scale reactor. From these tests, the link between the weight loss/gain of the samples and the reactivity at low temperature was confirmed, developing successfully two thermogravimetric tests to identify high risk samples. Afterwards, textural features of thermally altered coal samples (light reflectance and particle morphology) were studied by means of combined petrographic and image analysis techniques. Results showed that particle reflectance and textural changes depend on oxidation temperature, which are linked to the spontaneous combustion potential. Based on these results, two tests were proposed by comparing light reflectance before and after a slow oxidation, quantifying the formation of morphotypes associated with highly reactive samples. A similar approach was used to study biomass and coal-biomass blends, focusing on the quantification of intrinsic reactivity and particle morphology by TGA and optical microscopy. For raw and char biomass particles, results showed a significant correlation between the optical and reactivity properties. Additionally, several new morphotypes were identified from biomass char samples. These characteristics were associated with the thermal behaviour of large samples, although these results did not suggest any distinctive indicator to identify samples prone to self-heat, concluding that the low temperature oxidation of biomass is a completely different phenomenon to that experienced by coals. In the case of coal-biomass blends, the most relevant finding was a synergetic effect observed for the ignition temperature, which was always lower than the ignition temperature of the individual components. This finding has not been described in literature before, and further work is necessary in order to investigate this interaction in greater depth. Finally, a set of standardised procedures to assess the reactive properties of these materials has also been proposed.

The quest for ever stronger and tougher steels has lead to an interest in the 'Acicular Ferrite' microstructure, its chaotic and disordered morphology imparting a high degree of toughness to the steel. To date, only complex and expensive materials and manufacturing processes have formed acicular ferrite within bulk cast steel. As such, the thrust of this research is to produce a cheap steel addition, an iron - titanium oxide metal-ceramic composite, that will facilitate the formation of acicular ferrite in conventionally manufactured bulk cast steels. The Self-propagating High-temperature Synthesis (SHS) process has been utilised to manufacture the iron - titanium oxide material from compacts pressed from Fe203 + Ti powders. The fundamental reactions that occur as titanium powder and Fe203 + Ti powder compacts are heated in air and argon atmospheres have been investigated. The process’s involved are reported and have been modelled mathematically. A computer simulation of the reaction process has been developed and tested against experimental evidence. The effect of various compact parameters, the starting compact stoichiometry and other processing variables have been examined with respect to the composition of the products and their morphology.

This research project focuses on the application of numerical modelling methods to rock mechanics problems, combining theoretical, experimental and numerical modelling work. Specifically, practical finite difference modelling approach for analysing shaft lining stability through the Marl and Potash strata at Boulby mine UK has been developed using the commercially available software FLAC2D/FLAC3D (ITASCA 2008). A soft rock Marl occurs close to the bottom of the two deep shafts at the mine. Both shafts concrete linings through this stratum have suffered considerable pressure, which has caused gradual failure of the shaft lining. So far, both shaft linings through the Marl stratum have been restored twice after sunk in 1970s and a further third relining is now required and being planned. The in situ observations, the rock engineers's experience, and the available in situ measurements at the mine have been significantly helpful in the validation of the numerical modelling. Many factors at the mine site have, however, made this numerical modelling research challenging, including complicated lining structures, complex lining failure conditions and the scarcity of laboratory test data for the weakest rock material - the Marl, which easily weathers on exposure. Based on a comprehensive literature review, a database of materials properties relevant to this research has been produced. The methodology of obtaining appropriate rock mass input material properties to use in numerical modelling based on laboratory test data has been studied. In three-dimensional models in this research, two modelling methods have been developed to simulate each stage in the shaft linings: the continuous model for all shaft linings and independent models for each shaft lining. The numerical modelling results imply that: Firstly, in the independent three-dimensional models, the modelling results were difficult to understand due to the complexity of the structures representing the shaft relining systems and difficulty in defining appropriate properties for the interface elements. Therefore, the continuous three-dimensional model that gives the analysable modelling results is recommended by the author for this research. By this method, the effect of the historic changes in the stress field on each shaft lining's stability can be investigated from initial shaft construction to subsequent relining phases. Secondly, the weak rock Marl should not be the only reason for the shaft linings' failure through this stratum. The roadway approximately 10 m beneath the Marl stratum was also a key factor for the stability of the shaft linings. The weak Marl cannot carry the stress redistribution around the shaft caused by the roadway excavation, which was an uneven loading acting on the circular shaft linings. This uneven loading introduced high shear and tensile stresses which threatened the stability of the circular concrete structures. Thirdly, the interface materials between high strength concrete blocks in shaft relinings improved the flexibility of the lining systems successfully, but decreased the strength of the whole lining systems as weak "joints". In addition, the single ring concrete blocks (the first and third relinings) are a more effective lining than the double rings (the second relining), and the third relining would perform better than the previous ones. As a recommendation for the further simulation, it is worth attempting to simulate the longer term deformation and stress conditions of the shaft concrete lining systems using the Creep model built in FLAC2D/FLAC3D codes. Additionally, deeper research work combined with in situ investigation can be done to decrease the uncertainty of the input material properties to make the numerical models as close to the real engineering situation as possible.

The current trend towards the adoption of retreat longwall mining methods and the associated rapid development of the access drivages has exacerbated the environmental conditions experienced within these workings. The combined use of roof bolt and continuous miner systems has improved the face advance rate within rapid development drivages. In order to maintain adequate dust and gas control it is essential that the auxiliary ventilation and monitoring systems are correctly installed and maintained. The causes of many potential environmental hazards experienced within auxiliary ventilated rapid development drivages, are often attributed to a failure by the workforce and supervisory officials to maintain the correct installation, maintenance and operational standards of the ventilation and mining systems. The potential ventilation hazards encountered may include: the failure to deliver the required fresh air quantity and velocity to rapidly dilute and disperse methane gas liberated in the vicinity of the cutting face, or the failure to maintain sufficient exhaust air quantity in the vicinity of the cut to adequately capture dust produced on cutting and loading of the extracted mineral. Results of recent research studies have demonstrated that validated Computational Fluid Dynamics (CFD) simulation models can adequately replicate examples of good and bad ventilation. CFD models may be constructed and solved to examine the relative ventilation benefits produced by alternative mining and auxiliary ventilation configurations. These models enable the practitioner to predict and visualise the velocity, pressure and contaminant fields within an auxiliary ventilated drivage. This research project has developed a prototype educational aid, which animates and visualises these airflow and pollutant dispersion patterns within a Virtual Reality (VR) model. By introducing a pollutant such as methane into the CFD models, the VR simulation highlights regions of potential methane concentration build-up to the trainee. The application also allows the user to select/investigate the environmental consequences of enacting a number of remedial actions.

Palaeocene high-latitude coals from the Todalen Mbr. Central Tertiary Basin, Svalbard present an opportunity to understand the processes which controlled Arctic peat formation. Coals from this region have produced sub-economic quantities of bitumen during the 1920’s. Previous palaeogeographic models show significant variation between studies favouring deltaic and tidal wetland conditions. In addition, coal geochemistry studies have been limited to characterisation with little integration with palaeogeographic studies. This study utilises a large database of drill-logs to create cross sections and coal isopach maps to examine the spatial relation between seam thickness and palaeotopography. Palaeotopography is defined by mapping a ‘valley indicator’; the Grønfjorden bed, a fluvial conglomerate representing the first Palaeocene sedimentation. In addition, organic petrology organic and inorganic geochemistry were applied to samples from two mine sections and two boreholes to examine how coal quality and oil potential changed both within and between seams. The cross sections and isopach maps reveal that landscape had a significant but diminishing control upon peat accumulation. Thickest peats consistently formed at the break-in slope whilst topographic lows acted as areas of preferential channel formation and conduits for clastic sedimentation. Evolution of the landscape control had a significant control upon groundwater supply. As landscape control decreased the coals moved from isolated, raised bogs (Svea Seam) to laterally expansive minerotrophic fens (Svarteper and Askeladden Seams). Evidence of increasing marine influence and higher groundwater input was also observed from the Svea Seams to the Askeladden seam. In the Svea Nord and Longyear seam, supply of lithophile elements (Al, Ti, Na, K) is shown to be controlled by dust supply controlled by orbital cyclicity. By the Svarteper/Askeladden period lithophile element concentrations are controlled by clastic supply. Ca, Mg and Fe appear to be derived from groundwater. Sulfur concentration primarily reflects the supply of marine sulfur. Upper Todalen coals (Longyear, Svarteper and Askeladden) have significantly more oil potential than the Svea Seams with estimated retorting yields of 170-190kg/ton vs. 50kg/ton respectively. The Longyear seam exhibits relatively high HI values (ca. 300-400 mg/g TOC) consistent with a mixed Type II/III kerogen source. Greatest oil potential is shown to be favoured by formation within a fen environment, with high bacterial degradation (>100μg/g TOC hopanes), marine influence (>0.5wt% sulfur, Fe/S <0.9) and the unique temperate high lattitude Palaeocene climate of Svalbard, leading to preservation of hydrogen rich organic matter via organo-sulfur bond formation.