Affichage des articles dont le libellé est Mining engineering. Afficher tous les articles
Affichage des articles dont le libellé est Mining engineering. Afficher tous les articles
mercredi 3 août 2016
mardi 2 août 2016
vendredi 26 octobre 2012
mardi 25 septembre 2012
Development, Characterization and Application of a Reactive Bulking Agent for Wall Control
| Authors: | Silva, Guillermo C.O. | ||||||||||
| |||||||||||
| Keywords: | Low density explosives LDE | ||||||||||
| Issue Date: | 2007 | ||||||||||
| Series/Report no.: | Canadian theses | ||||||||||
| Abstract: | This research thesis is focussed on the development of a novel low density explosive composition whose main application is wall control in open pit mining. The product has, however, the potential to be used in a variety of applications and rock conditions where customization of the explosive’s energy output is required. Experimental observations on the novel low density explosive showed that the product is capable of initiating and sustaining stable detonations at densities as low as 0.10 g/cm3. Given the extreme low densities at which the novel product maintains its detonating characteristics, it will be appropriate to treat it as a reactive bulking agent, hence its name: Low Density Reactive Agent or LDRA for short. When mixed with standard ANFO prills, the reactive nature of the LDRA ensures a detonable mixture regardless of the final dilution sought or the degree of segregation eventually produced during mixing and loading. If operational constraints are such that a lower energy is required, the LDRA can then be used on a stand‐alone basis, without mixing it with other explosive compositions, such as ANFO or emulsions. The detonation characteristics of the LDRA at a target density of 0.15 g/cm3 were evaluated, with particular effort placed on measuring the detonation and explosion pressures, parameters having the greatest influence on damage. The effects of diameter, confinement and primer on LDRA performance were evaluated through velocity of detonation (VOD) measurements. In addition, VOD experiments were conducted in the LDRA to evaluate the stability of propagation in longer columns, the behaviour in a decking configuration and the ability to initiate and be initiated by a column of ANFO. The low pressure regimes characterizing the LDRA provided the opportunity to investigate the full pressure history of the detonation gases by designing experiments of a non‐destructive nature that allowed the repetition of tests under different loading scenarios. Following the characterization stage, the opportunity to test the LDRA as a damage control tool under a true operational scenario arose at the Chuquicamata Mine, in northern Chile. The project provided important input as to the feasibility of manufacturing the LDRA at a semi‐industrial scale and to evaluate the performance of the product in the large diameter blastholes used at the mine | ||||||||||
Stochastic Dynamic Optimization of Cut-off Grade in Open Pit Mines
| Authors: | Barr, Drew | ||||||||||
| |||||||||||
| Keywords: | Real Options Mine planning Economics Mine design Mine evaluation Cut-off Hedging Simulation Finance Mine optimization Valuation Mining Optimization Stochastic Cut-off grade | ||||||||||
| Issue Date: | 1-May-2012 | ||||||||||
| Series/Report no.: | Canadian theses | ||||||||||
| Abstract: | |||||||||||
Alkali Hydride-Borohydride Solutions for the Application to Thermally Regenerative Electrochemical Systems
| Authors: | Aubin, Ryan Nicholas | ||||||||||
| |||||||||||
| Keywords: | Thermally regenerative electrochemical systems Hydride-borohydride liquid mixtures Pressure differential thermal analysis Waste heat recovery | ||||||||||
| Issue Date: | 2009 | ||||||||||
| Series/Report no.: | Canadian theses | ||||||||||
| Abstract: | This thesis was concerned with the proof of concept for mid-grade, 250-500oC, industrial waste heat recovery using a thermally regenerative electrochemical system. Proposed thermally regenerative electrochemical systems are limited to high operating temperatures (> 900oC) and suffer from poor conversion efficiencies (< 20%). As such, a single chamber design that is free of moving parts was presented in this work. The concept for this novel regenerative system relies on gravity and a liquid medium to convey dissolved sodium hydride in a hydride-borohydride solution from cold to hot regions in a continuous circuit. Such a liquid transport medium could allow for operation below 500oC while stabilizing the hydride from thermal decomposition. Investigations on this system were carried out using a custom pressure differential thermal analyzer that was able to operate above temperatures of 700oC and pressures of 2.2MPa. The results of the experiments provided valuable information concerning the phase diagrams of various hydride-borohydride mixtures. The eutectic composition of the NaH-KBH4 system was found to be 43 mole% NaH. The corresponding eutectic temperature (503oC) was determined using the differential cooling curves. Appreciable NaH decomposition was noticed in mixtures above 59.0 mole% NaH. Mixtures up to 42.5 mole% KH in KBH4 were also investigated. The eutectic composition of the KH-KBH4 binary system was determined by extrapolating the liquidus curve to intersect the solidus curve. The KH-KBH4 eutectic temperature was found to be 390oC at 66 mole% KH. The experimental work successfully demonstrates that thermally unstable hydrides can be obtained in the liquid phase below their melting points, under moderate pressures, when mixed with alkali borohydrides. This significantly lowers the achievable operating temperature of the thermally regenerative electrochemical systems currently proposed. The use of the single chamber design with a hydride-borohydride liquid medium offers numerous advantages including: reduced maintenance, reduced operating temperature, reduced system weight, reduced parasitic losses, increased voltage, and increased reliability. The viability for mid-grade industrial waste heat recovery requires construction of a prototype which optimizes power outputs and explores the hydrodynamic transport of material. | ||||||||||
The recovery of magnesium oxide and hydrogen chloride from magnesium chloride brines and molten salt hydrates
| Authors: | de Bakker, Jan | ||||||||||
| |||||||||||
| Keywords: | Extractive metallurgy Nickel Magnesium chloride Molten salt hydrates Brines | ||||||||||
| Issue Date: | 2011 | ||||||||||
| Series/Report no.: | Canadian theses | ||||||||||
| Abstract: | Hydrochloric acid leaching of saprolite nickel ores has been proposed as an effective means of recovering nickel and cobalt. However, the leach produces a concentrated brine of magnesium chloride which must be hydrolyzed to recover the HCl lixiviant. The processing of carnallite similarly produces a concentrated MgCl2 brine; converting this brine into HCl and MgO provides an attractive way of adding value while effectively disposing of this waste product. Direct pyrohydrolysis of magnesium chloride brines by the reaction, MgCl2,a + H2Oa MgOs + 2HClg is energy-intensive as large volumes of water must be evaporated. The energy cost is high, and the HCl stream produced is limited to approximately 20 wt% HCl. This thesis explores alternative methods of obtaining HCl from aqueous magnesium chloride solutions. Two methods are considered: the hydrolysis, under autogenous pressure, of concentrated MgCl2 molten salt hydrates; and the precipitation of magnesium hydroxychloride compounds such as 2MgO·MgCl2·6H2O and 3MgO·MgCl2·11H2O, which are subsequently decomposed at high temperature. Considerable experimental difficulties were encountered in studying pressure hydrolysis of molten salt hydrates, despite extensive equipment modifications. Ultimately, the work moved on to precipitation and decomposition of hydroxychlorides. This was found to bear promise, and conceptual flowsheets based on these reactions are presented. A phase stability diagram giving the areas of predominance of the different hydroxychloride phases is presented, and fundamental thermochemical data are derived. The results of a kinetic study on magnesium hydroxychloride thermal decomposition are also presented. | ||||||||||
An Investigation of Leaching Chalcopyrite Ore
| Authors: | SCHAMING, JAMES | ||||||||||
| |||||||||||
| Keywords: | Chalcopyrite Heap Leaching | ||||||||||
| Issue Date: | 2011 | ||||||||||
| Series/Report no.: | Canadian theses | ||||||||||
| Abstract: | The abiotic leaching behavior of a chalcopyrite ore, from Asarco’s Ray-Mine, was conducted in shake flasks and miniature columns at elevated temperatures. The shake flask tests, with an ore particle size of 1.18mm-2.38mm, found the highest Cu extraction was obtained using 1M NaCl in a 9.8g/L sulphuric acid solution at 60°C, with 69% Cu extracted in 16 days. The next highest extraction, 59% Cu extracted in 16 days, was achieved by adding fine pyrite at a 4:1wt ratio with the chalcopyrite content, in a 9.8g/L sulphuric acid solution at 60°C. Flask tests using other lixiviants and additions found copper extractions in the range of 30-40% Cu after 16 days. In the mini-column tests, the rates of copper extraction were similar for all test conditions. The rate of Cu extraction, even with a small particle size of 1.18mm-2.38mm and an elevated temperature of 50°C, was slow for all test conditions with an average rate of ~0.15% Cu per day. The conceptual engineering of a hot, abiotic heap-leach for low-grade chalcopyrite ore, including hypothetical heat and mass balances was conducted. The leaching time for a commercial operation was estimated from published data on laboratory column leaching of chalcopyrite ores and extrapolated to a commercial heap-leach by analogy with known leaching times for chalcocite ores. In commercial abiotic heap-leaches of chalcopyrite ore, the partial oxidation reactions generate insignificant heat to maintain an elevated heap temperature therefore the heat required to maintain the elevated temperature must be provided externally. In commercial biotic chalcopyrite heap-leaches, the in-situ total oxidation reaction generates more heat than the abiotic reactions but is still insufficient to rapidly raise and maintain an elevated heap temperature. For a low-grade Chalcopyrite heap-leach the most practical method of providing this heat is by injecting steam into the base of the heap using current air injection pipes. An external oxidant is required and for an abiotic heap-leach external ferric generation will be required. | ||||||||||
An Experimental Investigation of the Effect of Blasting on the Impact Breakage of Rocks
| Authors: | Kim, Seok Joon | ||||||||||
| |||||||||||
| Keywords: | Blasting Impact Breakage of rocks | ||||||||||
| Issue Date: | 2010 | ||||||||||
| Series/Report no.: | Canadian theses | ||||||||||
| Abstract: | Size reduction represents one of the most energy-intensive and costly processes in the extraction of valuable minerals and rocks. Drilling and blasting, being the first operation in the size reduction chain, may have a significant downstream effect, influencing mine economics. This thesis investigates effects of blasting on subsequent size reduction operations. A series of small scale blasts have been conducted, and the fragments have been screened, drop weight tested, crushed and their Bond Work Index and breakage parameters have been determined. The process was repeated for 3 different types of granite blocks (Stanstead, Laurentian, and Barre granite) using samples not blasted previously and samples blasted with three different powder factors (0.391, 0.782, and 1.173kg/m3). As well, four types of different charge methods with the same powder factor were used to investigate the influence of blasting energy distribution on grindability in the case of Barre granite. Subsequently, stress wave collision blasting and the effect of delay timing were tested under the same powder factor conditions. Generally, powder factor resulted in the most significant changes in the breakage parameters as well as fragmentation. The Bond Work Index showed a small decrease as a function of powder factor, which can be considered to be material dependent. There is indication that distribution of charge resulted in better grindability while fragmentation seems to be similar in both cases and better than when air decking was used. The results from Barre granite showed clearly that stemming affected fragmentation by producing finer fragments. | ||||||||||
THE SELECTIVE SULPHIDATION AND PHYSICAL UPGRADING OF NICKEL FROM A NICKELIFEROUS LATERITIC ORE
| Authors: | HARRIS, CHRIS | ||||||||||
| |||||||||||
| Keywords: | Upgrading Flotation Sulphidation Nickel Laterites | ||||||||||
| Issue Date: | 30-Jan-2012 | ||||||||||
| Series/Report no.: | Canadian theses | ||||||||||
| Abstract: | The processing of nickeliferous laterites to produce nickel metal is both complex and energy intensive. Since most laterites are found in remote regions, the capital costs for the infrastructure can exceed those for the process itself. The low temperature sulphidation of lateritic ores to produce an intermediate nickel concentrate for further processing offers a number of potential advantages, such as lower energy consumption and a relatively simple flowsheet. In this research, the sulphidation of a nickeliferous lateritic ore was investigated between the temperatures of 450-1100oC and sulphur additions of between 25-1000 kg of sulphur per tonne of ore. The experiments demonstrated that the nickel oxide within the ore can be selectively sulphidized to a nickel-iron sulphide. It was found that both the grade and the sulphidation degree largely depended upon the temperature and the sulphur additions, with temperatures above 550oC exhibiting the highest nickel sulphidation extents and grades. A DTA/TGA with mass spectrometer was used to further elucidate the nature of the phase transformations that occur upon heating of the ore, in the presence of sulphur. It was found that the Fe-Ni-S phase formed at low temperatures was submicron in nature and heating to temperatures of 1050oC-1100oC allowed for the growth of the sulphides to a d80 of up to 14 µm due to increased sulphide mobility, associated with the formation of a liquid sulphide matte with dissolved oxygen. Flotation studies conducted on 60 g samples showed that the sulphides formed respond to flotation with maximum grades of up to 6-7 wt% nickel being achieved and average grades of between 4-5 wt% nickel. Recoveries were approximately 50% on a sulphide basis and it was determined that the low nickel grades were due to the entrainment of magnetite fines. | ||||||||||
Development of a Hydrogen Producing Thermal Control for Chemical Hydrogen Storage
| Authors: | St. John, Adam | ||||||||||
| |||||||||||
| Keywords: | Hydrogen storage thermal control efficient reactor | ||||||||||
| Issue Date: | 2007 | ||||||||||
| Series/Report no.: | Canadian theses | ||||||||||
| Abstract: | This thesis investigated a potential improvement to hydrogen storage for fuel cells using a thermally efficient hydrogen storage method. The efficiency of the storage system was improved using a metal hydride system to act as a thermal control unit for an exothermic chemical hydrogen storage system. A cylindrical shaped “hybrid” reactor was created to allow hydrogen production from a sodium borohydride packed bed reactor and the metal hydride. Additionally, a custom built pressure-composition-temperature apparatus was built to record the amount of hydrogen desorption from the metal hydride while isolating the metal from potential poisons such as oxygen. Before using the chemical hydride packed bed, heat transfer through the reactor was studied using circulating water. The water experiments showed that an increase in heat flux to the reactor led to a faster desorption rate of hydrogen from the metal hydride resulting in a larger temperature drop throughout the reactor. After the operating characteristics of the hybrid reactor were studied, a 10 wt% solution of sodium borohydride was created and pumped through the packed bed to produce enough hydrogen for a 300 W fuel cell. The amount of heat produced from the packed bed portion of the reactor was significant, but temperatures levelled to around 80 °C. As expected, temperature control was directly proportional to the rate of hydrogen release from the metal hydride. On average, approximately 10% of the available heat energy was transferred to the metal hydride, and the hybrid reactor operated with gravimetric and volumetric energy densities of 0.27 kWh·kg-1 and 1.29 kWh·L-1 respectively. If the hybrid reactor is used solely to control peak temperatures, the amount of metal hydride necessary for thermal control could be decreased. Additionally, improvements in heat transfer as well as the hydrogen storage materials themselves would increase the energy density values further. When compared to other energy storage devices, the hybrid reactor without improvements is competitive as a backup power generator due to its silent operation and large volumetric energy density. Since the hybrid reactor can provide quiet and cool energy storage in a relatively small volume, it may become an effective and efficient means for hydrogen storage with limited improvements. | ||||||||||
An Investigation into the Sulphation Roasting of Enargite Concentrates
| Authors: | Chambers, Brandon | ||||||||||
| |||||||||||
| Keywords: | Roast Leach Electrowinning Enargite Enargite Concentrates Arsenic Arsenic Fixation Sulphation Roasting | ||||||||||
| Issue Date: | 22-Aug-2012 | ||||||||||
| Series/Report no.: | Canadian theses | ||||||||||
| Abstract: | Potential new ore deposits containing significant levels of enargite, a copper arsenic sulphide mineral, are being considered for development. The processing of high arsenic copper concentrates directly in copper smelters is difficult due to environmental concerns. This thesis investigates a process using sulphation roasting as an alternative method for processing enargite concentrates; copper is recovered from the calcine by acid leaching, gold is extracted from the leach residue by conventional cyanidation and arsenic is either fixed in the calcine or precipitated from process emissions. In this research, sulphation roasting between the temperatures of 300-800oC, with varying oxygen and sulphur dioxide partial pressures, was investigated. Experiments indicated that high levels of copper extraction, as well as arsenic fixation, could be achieved from the produced calcines through hydrometallurgical processes. At operating temperatures between 400-550oC copper sulphate, copper arsenate, iron sulphate, hematite and iron arsenate form in the calcine, as well as some arsenic being volatilized as arsenic trioxide. At processing temperatures between 475-575oC, greater than 80% of the arsenic was retained in the calcine as copper and iron arsenates. Copper arsenate would be weak-acid soluble and fixed in an effluent treatment plant along with arsenic captured in the wet-gas scrubber bleed solution. As operating temperatures increase above 650oC copper sulphates were converted into oxysulphates, oxides and ferrites, hematite production was favoured, and arsenic was primarily volatilized. Increasing the sulphur dioxide addition in the reaction atmosphere resulted in additional sulphate formation and increased sulphate stability at higher temperatures. Sulphation roaster heat balances were developed for calcines produced at two temperatures, 500 and 750oC. They indicated that while high copper extraction and arsenic fixation rates could be achieved, the sulphation roasting reactions are highly exothermic and significant cooling water would need to be added. Due to these issues, it is likely that partial roasting operations would be economically favourable in greenfield operations. However, niche applications of this process in operations with existing copper SX/EW facilities in good acid markets, have the potential to be economically favourable. | ||||||||||
Associated Sulfide Minerals in Thiosulfate Leaching of Gold: Problems and Solutions
| |||||||||||||||||||||||
Inscription à :
Articles (Atom)