Natural Resources Engineering - Doctoral theses

Permanent URI for this collectionhttps://laurentian.scholaris.ca/handle/10219/2077

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Design and verification of a Hydraulic Air Compressor as a CO2 capture and sequestration system.
(2023-08-17) Mahdavi, Maryam
As a result of human activities, the level of atmospheric carbon dioxide (CO2) has increased. Carbon capture and sequestration (CCS) technologies offer an effective approach for mitigating CO2 from various industrial process to reduce the global climate change effect. These technologies can be integrated into existing infrastructure with minimal disruption. This study reviews on post- combustion CO2 capture and sequestration techniques, with a specific focus on mineral carbonation process routes and their potential feedstocks. Mineral carbonation is an approach that mimics the natural weathering of rock, in which metal oxide-bearing materials, for instance natural silicate minerals (serpentinite, olivine) react with gaseous CO2 to form solid carbonates. This process takes place on geological time scales, but it can be accelerated by increasing the concentration of CO2 in a reactor through pressurization of the system. The purpose of this study was investigation of technical feasibility of a CCS process by means of a hydraulic air compressor (HAC). A series of experiments were conducted on the HAC pilot plant to investigate the potential of the system as a post-combustion CO2 capture system. Those experiences experimentally verified a one-dimensional steady-state model for two-phase bubbly flow. The verified bubbly flow model was used to compare the hydrodynamics and mass transfer characteristics of HAC downcomers and upward co-current flow bubble column reactors and to predict gas liquid mass transfer coefficients. The experimental results showed that the HAC is an effective technology for intensification of CCS processes due to its improved mass transfer performance compared to other mass transfer devices. While the high capital cost of HAC construction, following a general Millar (2014) design paradigm, limits applicability, the horizontal injector loop (HIL), developed in this thesis offers a new apparatus with similar gas compressor performance and reduced height, which would make the concept more accessible for capital restricted projects. A mathematical dynamic kinetic model is developed to simulate the kinetics of CO2 absorption into an alkaline solution in the HIL. This model makes a significant contribution in predicting the absorption rate under operating conditions beyond those achievable in experimental tests undertaken. In addition, this model can be used to guide the design of a new reactor and future experiments, making it a valuable tool for CO2 capture and sequestration activity. Carbon dioxide capture and sequestration by means of a HIL as a pressurized, continuous chemical reactor was also investigated experimentally. The experimental results demonstrated that the HIL has a credible potential for this purpose. These experiments were also simulated using the dynamic kinetic model, which showed good agreement with the experimental findings. However, some potential improvements to the dynamic kinetic model have been identified to enhance its compatibility with experimental conditions.
Modeling time-dependent deformation behavior of jointed rock mass
(2022-07-04) Wang, Mingzheng
Long-term stability analysis and stand-up time prediction of underground excavations are important in engineering design and construction. In this thesis, a numerical study of the time-dependent deformation behavior of jointed rock mass is presented. Firstly, creep deformation behavior of intact rock is studied numerically using the grainbased modeling (GBM) approach based on the Distinct Element Method (DEM). A grainbased time-to-failure (GBM-TtoF) creep model for intact brittle rocks is proposed to simulate creep deformations in the first two creep stages and time-dependent failure at the tertiary creep stage. Parameters of the TtoF model are calibrated using experimental data of Lac du Bonnet (LdB) granite. Simulations of the time-dependent deformation of rock pillars using the GBM-TtoF model are conducted. The influence of pillar shape (width to height ratio) and loading ratio (stress / strength) on the time-dependent spalling on pillar walls is investigated. Secondly, creep deformation of rock joints is simulated by using the grain-based joint models that are established using the GBM-TtoF model. The influences of joint roughness and loading conditions (normal and shear stresses) on the long-term shear strength and creep sliding velocity of joints are investigated. A new creep model is proposed, which can be used to control the creep deformation behavior of flat joints in the DEM. The model is validated using experimental data of joints. Thirdly, a creep model for jointed rock masses, which can consider time-dependent deformations of both rock and joints, is proposed. Creep deformations of jointed rock masses are simulated using a few jointed rock mass models, i.e., a rock mass model with a single joint, a jointed pillar model and a high rock slope model. The creep deformation characteristics of the jointed rock mass models are analyzed. Finally, time-dependent deformation behaviors of tunnels excavated in jointed rock masses are simulated using the creep model for jointed rock masses. The weakening of face-effect due to creep deformation of the rock mass is modeled using the internal pressure reduction method and the convergence-confinement method. The stand-up time of unsupported tunnels is simulated considering the influence of rock mass quality and the unsupported roof span. The simulated result is validated using Bieniawski’s stand-up time chart. The models developed in this thesis provide novel numerical approaches to simulating creep deformations of rock, joints and jointed rock masses, and are important for improving the understanding of the time-dependent deformation behavior of jointed rock masses.
Uncertainty-based mine planning framework for oil sands production scheduling and waste management
(2020-06-18) Maremi, Ahlam Ramadan
In open pit mining, the most significant challenge is determining the optimum long-term production schedules that maximize the project value by providing ore to the processing plant at full capacity while satisfying all required constraints. For oil sands strategic mine planning and waste management, as mining advances in a specified direction, in-pit tailingscells’ dyke footprints are released for dyke construction. The dykes are constructed from overburden, interburden and tailings coarse sands dyke materials which come from the mining operation. The construction of in-pit (and ex-pit) tailings impoundment dykes therefore needs to be well integrated with the waste management strategy to ensure regulatory compliance and sustainable mining. In this research, an uncertainty-based mathematical programming framework is developed based on mixed integer linear goal programming (MILGP) model for oil sands production scheduling and waste management. The effect of grade uncertainty on production schedules is investigated. The grade uncertainty financial risk associated with a production schedule is minimized using kriged estimates with a variance penalty scheme. This investigation is based on the concept of mean-variance analysis, which is the process of weighing variance (risk) against the expected net present value (NPV). Subsequently, the impact of organic rich solids (ORS) content on bitumen recovery during processing is also studied. ORS content is used to predict ore processability in addition to the traditional use of bitumen and fines contents, and its impact on NPV quantified. The developed MILGP model is implemented using new robust automated production targeting (APT) constraints that optimize the annual capacities for material mined and processed over the mine life. In addition, mining-cells are deployed for the generation of in-pit tailings-cells designs used as dedicated disposal areas for backfilling. Two main waste management approaches are used to implement the developed model. Implementation A; where the ultimate pit is divided into predetermined pushbacks as tailings-cells within the ultimate pit limit (UPL), and Implementation B; where the ultimate pit is divided into mining-cells that are used to generate in-pit tailings-cells designs. To verify the research models, three oil sands case studies were carried out. The first case study investigates the effect of grade uncertainty on production schedules. The technique applied is based on the concept of mean-variance analysis, which is the process of weighing risk (variance) against expected NPV. The model generates a range of NPV which represents the mining investment risk profile associated with grade uncertainty. The second case study explores the impact of ORS content on oil sands ore processability. The results showed a 3.46% overestimation of NPV arising from not taking into account the effect of ORS content on bitumen recovery during mine planning. The final case study examines the implementation of waste management strategies based on different size and number of unit mining-cells used in creating tailings-cells for backfilling. The results showed that, decreasing the volume of unit mining-cells used in creating the in-pit tailings-cells increases the NPV of the operation due to increased operational flexibility. Additionally, as the percentage of in-pit volume to be backfilled increases, more savings is generated from not sending tailings to external facilities at a higher cost. These results proved that the uncertainty-based MILGP model is a robust tool for optimizing oil sands long-term production schedules whilst taking into account grade uncertainty, ore processability and tailings-cells designs.
Open pit-underground mining options and transitions planning: a mathematical programming framework for optimal resource extraction evaluation
(2021-04-08) Afum, Bright Oppong
Near-surface mineral deposits that extend to great depths are amenable to both open pit mining and/or underground mining. The strategic planning of such mineral deposits often leads to several variations of open pit-underground (OP-UG) mining option(s) and transitions including (a) independent open pit (OP) mining, (b) independent underground (UG) mining, (c) simultaneous open pit and underground (OPUG) mining, (d) sequential OPUG mining, and (e) combinations of simultaneous and sequential OPUG mining. Notable limitations to recent developments in the OP-UG mining options and transitions optimization problem includes one or more of the following: a) lack of rigorous mining optimization approach, b) lack of solution optimality assessment, c) lack of geotechnical consideration for the mining options and transition zones, d) lack of consideration of exhaustive variables for essential UG mining complexes, and e) non-comprehensiveness and inefficiency of the implementation models. The main research objectives are 1) propose an optimization technique for OP-UG mining options and transitions planning, and 2) develop, implement and verify a theoretical optimization framework based on Mixed Integer Linear Programming (MILP) model to determine: a) the most suitable mining option(s) to exploit an orebody; b) the position of the required crown pillar, time and order of development of primary and secondary accesses and main ventilation opening, and the schedule of geotechnical support of the secondary development accesses and stopes if UG mining option is considered; and c) the ore and waste extraction schedules that maximizes the net present value (NPV) of the mining project. MATLAB programming platform was chosen for the MILP formulation implementation and a large-scale optimization solver, IBM ILOG CPLEX, was used for this research. The MILP formulation was tested and implemented with an experimental copper dataset and two real gold deposit case studies. The first case study verified the appropriateness of the optimization technique and strategies used in the MILP framework for open pit-underground mining options and transitions planning. The second and third case studies are implemented with stockpile management and multiple essential underground infrastructures to enhance practicality and rigor of the MILP model. The third case study was additionally evaluated with industry standard software, Whittle, and the results compared to that from the MILP model. The MILP model scheduled the deposit with combined sequential and simultaneous OPUG mining over 8 years mine life while Whittle scheduled the deposit for OP mining over a mine life of 20 years. The NPV generated by the MILP model was $ 4.01 billion while the NPV generated by Whittle Milawa NPV algorithm was $ 2.31 billion, representing about 42.4% loss in financial benefits. The stripping ratio from Whittle OP mining was 2.79 compared to 0.34 from MILP model for the OPUG mining. Analysis of the results showed that, the MILP model significantly avoids the mining of excessive waste to uncover mineralized material by switching from OP to UG mining option. This MILP framework implementation for extraction of deep-seated near-surface deposits demonstrate potential value to a mining project at the prefeasibility stage when the global mining options decisions are guided by a rigorous optimization process. The MILP framework do not evaluate the impact of varying crown pillar dimensions on the mining options.
Adaptation of microalgae bioprospected from stressed environments in Northern Ontario for the production of lipids
(2020-12-16) Desjardins, Sabrina Marie
Photosynthetic green microalgae are a promising bio-feedstock that can be used to generate lipids for transesterification into biodiesel and/or various human health products such as polyunsaturated fatty acids. Unfortunately, due to their cultivation requirements, such as high energy requirements and carbon dioxide (CO2) as a carbon source, large-scale biomass production generally remains uneconomical. To address this issue, the use of industrial flue gas as a low-cost source of CO2 and a biorefinery approach to help mend the economic burden of microalgae-based products with an emphasis on creating co-products from lipid-extracted biomass (LEB) are assessed in this thesis. Microalgae’s ability to sequester CO2 through photosynthesis is also advantageous in mitigating harmful industrial emissions. While these flue gases can have high concentrations of CO2, they also can contain numerous contaminants (e.g., heavy metals, particulate matter) that discourage microalgae growth, and therefore their ability to fix CO2. But, the most significant issue can be high nitrous oxide (NOx) and sulphuric dioxide (SO2) concentrations within a flue gas that cause acidification when bubbled through liquid media. It is due to this acidification that finding the productive microalgae species to grow in those systems can be problematic. To address this, bioprospecting acid-tolerant microalgae from low pH environments in active and non-active mining sites was explored and the acidophilic species present identified through DNA sequence analysis. Bioprospected algal species were then grown in acidic conditions similar to those created by bubbling flue gas from a nickel smelter into water (pH 2.5). From this work, it was found that the acid-tolerant green microalgae in the genus Coccomyxa acclimated to the acidic conditions with suitable growth rates (0.136 day-1) and biomass production (25.71 mg L-1day-1). However, anabolic production of target biochemical molecules, such as lipids, is the key step in the bio-product process. It is known that microalgae have the ability to accumulate bioactive compounds when placed in stressed environments, such as high illumination and low nutrient availability, but little is known an about the impact of low pH and in particular the lipid composition of acidophilic microalgae. Research confirmed that the lipid compositions of bioprospected acid-tolerant microalgae was in the target range (13%). However, further work showed that an increased total lipid content (up to 27%), with a desirable rise in the relative level of health beneficial higher polyunsaturated fatty acid, could be achieved by applying dark stress at the end of the exponential growth phase. It is, therefore, proposed that this approach could be an easy, low-cost method to enhance lipid productivity
The effects of automation on the environmental impact of deep underground metal ore mining operations
(2020-10-27) Moreau, Kyle Steven
The growing demand for increased production has resulted in the need to develop deeper underground mines to extract more resources. However, the mining process becomes less economically attractive as the ventilation and ore transportation costs drastically increase when operating at large depths. This has led to the industry investigating automated battery-electric and biodiesel fueled machinery instead of diesel machines to reduce emissions, and hence ventilation costs, as well improve productivity and thereby, the economic viability of deep mine projects. A life cycle assessment (LCA) approach has been developed to evaluate the environmental impact from introducing automated equipment in underground copper mines. This is a novel application for an LCA, and as a gauge of model accuracy, it was found that calculated greenhouse gas (GHG) emissions for an underground mine site in Canada were within 5.6% of their reported emissions. The model was then expanded using data collected from automation trials at a Canadian mine to predict changes due to the introduction of various levels of automation with regards to the impact potentials of global warming, acidification, eutrophication and human toxicity. All impact levels were quantified and found to decrease due to automation. Data from this site study was then used to further develop the LCA model to predict changes in environmental impacts for underground copper mine sites in Australia, Canada, Poland, USA and Zambia. Site specific parameters and processes that contribute to their overall environmental impacts were identified, and the calculated CO2 emissions were within 4.2-5.6% of the reported values. The mining industry is moving toward introducing significantly more technology to enhance both productivity and safety. This thesis investigates using an LCA approach to add a third dimension; improved environmental impacts that contribute to more sustainable mining
A framework to develop a hybrid methodology for modeling of diesel particulate matter concentration in underground mine ventilation systems
(2019-10-15) Zhang, Hongbin
The purpose of this research is to develop a hybrid methodology for diesel particulate matter (DPM) modeling for underground mine ventilation systems. The hybrid methodology, which is an enhanced and complementary tool, is proposed to provide improved diesel input to a ventilation network solver by using a computational fluid dynamics (CFD) solver. The hybrid methodology uses the DPM results from a calibrated CFD model to update those from a network model at shared locations. A CFD approach for simulating DPM over an extended period has been proposed to make the hybrid methodology more adaptable to large ventilation systems. With the proposed CFD modeling approach, contaminants like DPM can be modeled accurately in a timely manner over an extended period of time. The results from this approach are then used to update the network model results at the shared outlets. The workflow to update DPM results from the network model using the calibrated CFD model is presented. Two field studies were conducted in an underground mine in the western United States. Due to the low quality airflow and DPM data collected from the field, this study should be viewed as a qualitative study rather than a quantitative study. Corresponding CFD models, ventilation network models, and updated ventilation models were also established, and results from these models were compared with the experimental data. The limitations for both the instruments and the methodology were defined as well.
Study of mechanical properties of jointed rock mass using lattice-spring-based synthetic rock mass (LS-SRM) modeling approach
(2019-12-16) Bastola, Subash
With the recent development of high-end computation technology, it is feasible to use complex numerical modeling technique such as synthetic rock mass (SRM) modeling for the characterization of mechanical properties of rock mass. However, the SRM modeling approaches that have been used to date such as the ones based on bonded particle and bonded blocks cannot properly incorporate realistic discontinuity surface geometry (waviness and roughness) into the numerical model and discontinuities are often simplified as having planar surfaces. Models with simplified planar discontinuity surfaces do not represent the true geometry and physics of the natural discontinuities which raises the question on the reliability of the geotechnical parameters resulting from these models. It is widely known that the inherent surface roughness significantly influences the shear strength and stiffness of a non-planar discontinuity. The goal of this thesis is to develop numerical models that can incorporate these natural undulating discontinuities for the determination of reliable estimates of strength and deformation properties of jointed rock masses. Three-dimensional lattice-spring-based synthetic rock mass (LS-SRM) models are generated by incorporating both planar and non-planar discontinuities to simulate the mechanical behaviors of both laboratory-scale jointed rock and mine-scale jointed rock masses. A calibration methodology is established by means of extensive sensitivity analysis of lattice model parameters. Studies are also conducted to understand the crack evolution mechanism (initiation and propagation) in precracked marbles with both planar and non-planar cracks. Influences of joint properties (orientation, intensity, persistence, and roughness) on the strength and deformability of jointed rock under compression are also investigated. Influence of rock mass scale on the strength and deformation modulus is investigated to determine the representative elementary volume (REV) of the rock mass. Using the REV sized rock mass, the influence of discontinuity intensity and confining pressure on the mechanical properties (strength & deformability) of jointed rock masses are also investigated. In addition, the influence of the pre-existing natural discontinuity of different configurations (waviness, intensity, size) and in-situ stress on slope stability and deformability of an open pit mine are investigated. Complex crack propagation mechanism is observed in the laboratory-scale pre-cracked rocks with non-planar cracks under compression. There is an increase in the strength and deformation modulus for the laboratory-scale jointed rock models with non-planar discontinuities, lower discontinuity intensity, and lower discontinuity persistence. Peak strength and deformation modulus of the rock mass decreases with the increase of discontinuity intensity. Peak strength of the rock mass increases with the increase of confining pressure. Slopes excavated in the rock mass with non-planar discontinuities are found to be more stable than the slopes excavated in the rock mass with planar discontinuities. Similarly, slopes excavated in the rock mass with larger discontinuity size and higher discontinuity intensity are less stable than the ones excavated in the rock mass with smaller discontinuity size and lower discontinuity intensity. It is also found that the slopes exhibited localized instabilities under the influence of high in-situ stress. The findings of this research aid in better characterization of the mechanical behavior The findings of this research aid in better characterization of the mechanical behavior of jointed rock mass and provide more reliable estimates of geotechnical design parameters.
Measuring and modelling human response to foot-transmitted vibration exposure
(2019-07-16) Goggins, Katie Anne
Foot-transmitted vibration (FTV) occurs when a worker is exposed to vibration through the feet and can occur when operating vibrating equipment such as bolters, jumbo drills, or crushers, or standing to operate mobile equipment such as locomotives and forklifts. Exposure to FTV has been linked to the development of vibration-induced white feet, a vascular disorder with reduced circulation to the toes causing blanching. Vibration research has been focused on whole-body vibration (WBV) and hand-arm vibration, with FTV being lumped in to standing WBV. This research includes, but is not limited to, resonant frequency identification, development of international standards governing safe exposure limits, personal protective equipment design, and model development. It is the intention of this research to initiate research specifically for FTV. The first step to preventing harmful exposure is to identify the resonant frequencies at different anatomical locations on the foot (Objective 1). The resonance of 24 anatomical locations on the foot was identified for 21 participants, where the most notable differences in the average peak frequency occurred between the toes (range: 99-147Hz), midfoot (range: 51-84Hz), and ankle (range: 16-39Hz). As workers do not normally stand in a completely natural position, it was equally important to measure how altering the location of the centre of pressure (COP) changes resonance and the transmissibility of vibration through the foot (Objective 2). The resonance at the same 24 anatomical locations was identified when the COP was pushed forward (towards toes) and backward (towards heels). Generally, resonance at the measurement location increased when the COP was concentrated to a particular portion of the foot. The third objective of this research was to reduce the measurements at 24 anatomical locations, from the first two objectives, down to a representative subset (Objective 3). Multiple correspondence analysis was conducted on the peak transmissibility magnitude in order to assess structure displacement leading to increases in potential injury risk. Transmissibility results were analysed based on two magnitude thresholds: at 2.0 indicating 100% amplification of the input signal, and at 2.5 indicating 150% amplification. Results indicate that transmissibility measurements at the nail bed of first phalange, head of first metatarsal, head of second metatarsal, and the lateral malleolus may be sufficient to effectively measure foot-transmitted vibration when participants changed their COP location from natural, forward and backward. Then a K-means analysis was conducted to minimize the anatomical locations necessary to capture the transmissibility response from 10 to 200 Hz, and using the reduced locations, a lumped-parameter model was designed and validated (Objective 4). Three locations (the nail of the big toe, the third metatarsal, and the lateral malleolus) were found to be sufficient for summarizing FTV transmissibility modulus. A three segment, four degrees-of-freedom lumpedparameter model of the foot-ankle system (FAS) was designed to model the transmissibility response at three locations when exposed to vertical vibration from 10 to 60 Hz. Reasonable results were found at the ankle, midfoot, and toes in the natural standing position and forward COP. However, when the COP is backward, the model does not sufficiently capture the transmissibility response at the ankle. Determining the resonant frequencies of the FAS is important for the prevention of vibration-induced injury. Resonance needs to be incorporated into the design of equipment, tools (e.g. anti-vibration drills, isolated platforms), and personal protective equipment (e.g. antivibration insoles or boots) can be modified to reduce vibration at the frequencies where tissue resonance occurs. These findings could also inform the development of new international standards for measuring/reducing exposure to FTV.
Synthesis, properties and applications of functional polymer nanocomposites
(2018-11-30) Huang, Lingqi
Polymer nanocomposites have been extensively studied and have found numerous applications as they provide versatile materials with substantially enhanced properties. Despite the enormous developments, design of novel value-added polymer nanocomposites with new superior functional properties through convenient low-cost synthesis remains a continuous challenge. This thesis demonstrates the alternative, simple design of several novel polymer nanocomposite systems with enhanced mechanical, surface, or catalytic properties. Firstly, a new method for the modification of cellulose nanocrystals (CNCs) is developed with the use of hyperbranched polyethylene ionomers containing cationic quaternary ammonium ions through an ionic interaction mechanism. A systematic study has been undertaken on the modification process and the modified CNCs. In contrast to original CNCs that can only disperse in water or few highly polar solvents, ionomer modified CNCs are able to disperse in several nonpolar or low polarity organic solvents. Dispersions of several modified CNCs in THF exhibit the unique thixotropic rheological behavior. The modified CNCs have also become dispersible in a commercial non-polar hydrophobic ethylene-octene copolymer (EOC) elastomer due to the presence of nonpolar polyethylene modification layer. Based on thermal, rheological, and tensile mechanical characterizations, EOC nanocomposites filled with the modified CNCs are significantly reinforced with nearly doubled tensile modulus relative to neat EOC while with a much better-maintained elongation at break relative to those filled with unmodified CNCs or surfactant-modified CNCs. iv Secondly, a class of CNC-sodium alginate (SA) nanocomposites derived exclusively from sustainable biopolymers has been designed to fabricate tough-strong nanocomposite film. A systematic study on the effects of composite composition on the optical, thermal, and mechanical properties of the prepared films has been undertaken. The calcium ion crosslinked composite films maintain high film transparency with higher thermal and mechanical properties than the uncross-linked films, indicating that the calcium ions play an important role in the enhancement of mechanical and thermal properties. The effects of various metal ions on film mechanical properties have also been studied. As a result, the bivalent calcium ions show the most optimum effect to render strong-tough composite films. Thirdly, hybrid composites of multi-walled carbon nanotubes (MWCNTs) decorated with polycyclopentene crystals have been synthesized by a novel in situ Pd-catalyzed cyclopentene polymerization technique. It is demonstrated that the method offers a convenient, large-scale, one-pot noncovalent surface decoration of polycyclopentene crystals on the MWCNTs. Controlling the catalyst loading and/or polymerization time in the polymerization effectively tunes the composition and morphology of the as-prepared hybrid composites. Interestingly, films made of the composites show the characteristic lotus leaf-like superhydrophobicity featured with high water contact angle (> 150), low contact angle hysteresis (< 10), and low water adhesion, while being electrically conductive. Lastly, a systematic study on ligand-assisted selective hydrogenation of alkynes (phenylacetylene and diphenylacetylene) over three Pd nanocatalysts have been presented with the purpose of identifying the most optimum ligands. Five ligands, including quinoline, pyridine, DMSO, 3,6-dithia-1,8-octanediol (DTO), and triphenylphosphine, have been v screened with their performance compared. It is demonstrated that the sulfur-containing DTO and phosphine-containing triphenylphosphine are the more efficient and practical ligands in improving the alkene selectivity of the catalysts.
Quantification of seismic responses to mining using novel seismic response parameters
(2018-10-05) Brown, Laura Grace
Mining-induced seismic events can be loosely classified as induced events or triggered events. Induced seismic events in mines are typically proportional to mining-induced stress change. This type of rock mass failure is often successfully managed by seismically active underground mining operations, and is generally considered part of a normal seismic response to mining. Triggered seismicity represents a disproportional seismic response to mining, and often results in visible rock mass damage. The variations in space and time characteristics of induced and triggered seismicity, particularly in relation to mine blasting, are indicative of distinct seismic source mechanisms and may be useful in seismic hazard evaluation for mines. In this work, Seismic Response Parameters (SRP's) are conceptualized using fundamental rock mechanics and mine seismicity principles, and subsequently supported with a comprehensive case study from Agnico Eagle's LaRonde mine. The primary factors considered in this thesis are space and time; how they relate a seismic response to the stimulus and how they relate individual events within a seismic response to the response itself. The four SRP's are: Distance to Blast, Time After Blast, Distance to Centroid and Time Between Events. A normalized set of SRP's, calculated with site specific considerations, are proposed as a meaningful measure of how likely a seismic response is to be induced or triggered by discrete mine blasting. Within this thesis, Seismic Response Rating (SRR), the summation of normalized SRP's, is presented as a means of quantifying seismic responses to mining with a single numerical value. Seismic responses at LaRonde mine are used to demonstrate the application of SRP's and SRR to real mine seismic data. A mine shutdown period, in which no mine blasting occurs, is used to provide meaningful insight into the spatial and temporal relations of mine seismicity. In the absence of mine blasting, seismic events associated with induced seismic source mechanisms cease to obscure triggered seismicity (resulting from triggered source mechanisms). Where and when both induced and triggered seismic source mechanisms interact in space and time, complex seismicity may be observed. An interpretation of complex seismic responses to mining, occurring in the transitional zone between induced and triggered seismicity, is also presented in this thesis.
Air entrainment and air-water separation in hydraulic air compressors
(2018-08-16) Hutchison, Alex
A hydraulic air compressor (HAC) is an isothermal gas compressor that uses hydropower to compress air, originally developed by Charles Taylor in the 1890s to supply industry with compressed air. In the modern revival of this technology, the hydropower will be provided by pumps rather than natural sources. As such, energy efficiency is an important driver of component design; all of the hydropower is consumed either to overcome irreversibility or to compress air. The compressor relies on the increasing pressure of water flowing downward in a downcomer to compress air in the form of bubbles being dragged along with the flow. The air entrainment process at the top of the downcomer is facilitated by a mixing head. At the bottom of the downcomer, the bubbles are separated from the flow in a separator vessel. The objective of this thesis is to develop the design methodology for the air entrainment and air-water separation components on either end of the downcomer process. Several mixing heads were tested on a small (4.5 m height) prototype HAC. The test without a mixing head successfully entrained air, confirming that air entrainment is a system effect. Two heads with dissimilar geometry were associated with the lowest irreversibility, leading to the conclusion that the best design at that scale is a mixing head incorporating some form of vortex breaker. Air entrainment is driven by a system energy balance and not exclusively by a local Venturi geometry. The fraction of the air successfully captured in the plenum of the separator is called the separator effectiveness. Mechanistic models have been created to characterize both the irreversibility and separator effectiveness of two types of gravity separator (horizontal and vertical orientation) for iv the design of separators for future commercial-scale compressors. The separator effectiveness models require as input the flow field information from computational fluid dynamics analysis and the bubble size distribution at inlet. The bubble size distribution was measured on the small prototype and used to select a bubble size prediction model for testing on a much larger scale (29 m height) demonstrator HAC. The displacement model for horizontal separators matched the actual performance at the prototype scale well, particularly at high flow rate. The vertical velocity model produced a good match for the separator on the demonstrator HAC, but not for the same bubble size model identified on the small prototype.
Characterization of seismic sources using sequential spatial clustering and fractal dimension
(2018-07-30) Cortolezzis, Donna Marie
Despite years of research, unexpected seismic events in mines continue to cause damage and loss to people, equipment, infrastructure, and reserves. This research uses novel approaches to characterize the locations, times, and intensity of seismic events for four known seismic sources. The seismic source case studies are the development of a ramp, the abutments around a zone of stopes, a failing stope pillar, and a shear zone adjacent to an orebody. Each seismic source is characterized by sequential spatial clustering, and the fractal dimension of the seismic source parameters of location, time and intensity. The novel application of sequential spatial clustering preserves the sequence of events within a cluster. The method can be used at any point in time which means as a rock mass changes the seismic response is expressed and identified very early on. Once identified, it allows the opportunity for investigation and decision making to take place as the rock mass changes in an unexpected manner. The application of fractal dimension to seismic source parameters revealed that the fractal nature of a parameter is not infinite but exists within a range. The fractal range reflects the character of a seismic source. If some events occur outside the fractal range they also provide important information about the history of the seismic source that occur less often than the fractal range but are still possible. This research has expanded the knowledge of when, where, and how intense seismic events can be expected for four seismic sources using a new sequential spatial clustering method and fractal dimension characterization.
Dynamic modelling of catalytic SO2 converter in a sulfuric acid plant of an industrial smelter
(2018-04-16) He, Jianjun
In industrial nickel and copper production, sulfur dioxide (SO2) is generated from the combustion of sulfide ores. With increasingly tightened regulations on SO2 emissions, a sulfuric acid plant has become a crucial part of industrial smelters. It converts environmentally harmful SO2, which is generated in smelter furnaces, roasters, and Cu-reactors, into commercially beneficial sulfuric acid. This method is recognized as one of the most effective ways to ensure that smelters are able to satisfy the SO2 emission regulations. A sulfuric acid plant is primarily comprised of a central catalytic SO2 converter, SO3 (sulfur trioxide) absorption towers and a series of interconnected heat exchangers. The catalytic SO2 converter is the key component and the focus of this research. Both steady-state and dynamic models of the converter are developed in this thesis. A steady-state model of the converter is established in accordance with steady-state mass and energy balances. The developed model provides an explicit relation between SO2 conversion ratio and gas temperature, which is denoted as the heat-up path of the converter. By combining the heat-up path with the equilibrium curve of the SO2 oxidation reaction, an equilibrium state for every converter stage can be obtained. Using the developed steady-state model, simulations are performed to investigate the effect of inlet SO2 molar fraction and gas temperature on the equilibrium conversion ratio. In an industrial SO2 converter, the SO2 concentration and conversion ratio out of each bed are important variables but are not measured in real time. To monitor these unmeasured variables in industrial operations, a soft sensor is proposed by combining the derived steadystate model with dynamic data analysis. The obtained soft sensor provides a real-time estimation of outlet SO2 concentration and the conversion ratio from measured temperatures. For synchronization between the inlet SO2 concentration and outlet temperature, a first-order exponential data filter is applied to the feed SO2 data. With the filtered signal being used, the proposed soft sensors give a satisfactory estimation of both outlet SO2 concentration and conversion ratio in the converter stages. Dynamic modelling is carried out using two different model forms: ordinary differential equation (ODE) and partial differential equation (PDE) models. The ODE model is obtained by applying dynamic mass and energy conservation to the SO2 converter. The resulting model can be used in industrial applications and describes the converter performance even if information of reaction kinetics is not available. A good fit with collected industrial data verifies the validity of the developed ODE model. The effect of process input variables is studied using simulations with the ODE model. Dynamic modelling is performed by implementing mass and energy balances on both fluid and solid-phase gas flows. The proposed two-phase dynamic model, which takes the PDE form, is able to generate detailed profiles of the SO2 converter within time and space. With the estimated parameters, this two-phase dynamic model generates a good fit between the simulated and measured outlet temperatures. Based on the PDE model, simulations are run to investigate the detailed mechanistic performance of the converter. The detailed PDE model provides useful explanation of, and prediction for the converter behaviour.
Cobalt-doped zinc oxide thin films as model Fischer-Tropsch nano-catalysts grown by pulsed electron beam ablation
(2017-12-05) Ali, Asghar
The production of materials in thin film form with unique properties is of growing scientific and technological interest. Zinc oxide is a low cost, and environmentally benign wide band gap semiconductor, which makes it an excellent supporting material for nanoparticles with a plethora of potential applications. Upon doping with Co and other transition metals, ZnO exhibits room temperature ferromagnetic properties with enhanced performance and new functionalities when used in thin film devices. Zinc oxide-supported cobalt nano-composites are promising materials with desirable catalytic properties making it an interesting material for use as an efficient nano-catalyst in many important reactive processes such as Fischer-Tropsch synthesis (FTS), photocatalysis, hydrogen production and steam reforming. Pulsed electron beam ablation (PEBA) has recently emerged as a potential technique for the fabrication of superior quality thin films. The production of well controlled nano-sized particulates is a characteristic feature of PEBA, which has a strong bearing on the surface morphology of the deposited films. In the current work, the potential of PEBA in the deposition of Co-doped ZnO thin films has been assessed and the critical process conditions that affect the growth of the thin films on different substrates have been thoroughly investigated. The main objective of the current work is to deposit Co-doped ZnO thin films via PEBA, and assess the potential of the deposited films as model nano-structured catalysts for the synthesis of green liquid fuels from syngas. PEBA has several advantages including modest requirements for vacuum, control of film thickness, easy set-up, low capital cost, reduced operation and maintenance costs, small footprint, enhanced efficiency, and relative safety (no toxic gases as in pulsed laser ablation or potential noxious by-products as in solvo-thermal routes) over other film preparation techniques. In this project, Co:ZnO thin films have been synthesized from a single target on various substrates. Numerous process parameters have been assessed such as substrate material, deposition temperature, electron beam voltage, beam pulse frequency. Targets of varying cobalt loads viz., 5 w%, 10 w%, and 20 w% have been investigated as well. The effects of pre and post annealing on the physico-chemical properties of the thin films have also been studied. The deposited films have been characterized using complementary analytical techniques such as xray diffraction (XRD), x-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), energy dispersive x-ray (EDX), visible reflectance spectroscopy (VRS), and atomic force microscopy (AFM). Such comprehensive analyses have helped in assessing the quality of the films and in guiding the experimental strategy in the quest to find the optimal process conditions. Finally, the films have been evaluated for their potential as model nano-catalysts for FischerTropsch synthesis in a 3-phase continuously-stirred tank slurry reactor (3-φ-CSTSR) using a Robinson-Mahoney stationary basket (RMSB). The results have been described in terms of activity and selectivity of the thin film nano-catalysts.
Production and characterization of polystyrene resins containing fine activated carbon particles
(2017-11-20) Hmidi, Nuri
The development of high capacity adsorbent using engineered activated carbon fines technology, and their ability to extract gold from solution is presented. The unique feature of these adsorbents is their ability to adsorb gold ions from low concentration solutions like mine effluent as well as from leached solutions in gold mills. Production of polystyrene ion exchange resins containing fine activated carbon particles denoted, PSAC, (Polystyrene Activated Carbon) and their gold stripping kinetics were studied. Polystyrene beads were prepared by simple suspension polymerization. However, addition of fine activated carbon (AC) during suspension polymerization was not successful in producing small beads, but rather a conglomerated mass, which was then broken up and shaped into smaller beads. PSAC beads were also produced by co-extrusion of polystyrene with activated carbon and by physical adsorption of activated carbon onto raw polystyrene beads in an autoclave at a temperature above the glass transition temperature of polystyrene. Stripping tests were performed which identified the latter bead type as being the most promising form of PSAC bead for future research. The work was aimed at optimizing the production of the beads in terms of their physical and chemical properties. This work led to the development of a new polystyrene/activated carbon ion exchange bead as an alternative to pure activated carbon. A mini-elution column was also designed to carry out the test work to study the performance of beads and loaded fine carbon stripping parameters under typical industrial conditions. Further development of this research may lead to a new method of stripping loaded fine carbon on mine sites as part of the existing gold milling and extracting circuits.
Production of cryogens using wind energy for use in deep mine cooling and ventilation.
(2017-09-05) Kunwar, Saruna
This research work, named as ‘CryoVent’, was focused on determining the feasibility of using wind energy, to produce liquefied gases (cryogens) continuously in a safe approach that can be used for the cooling and ventilation of underground mines. The experimental work performed suggested that the continuous production of liquefied gases with variable input work is practical. The average specific power consumption for liquefaction of nitrogen in this work was 7.86 kWh/kg using the refrigeration produced by helium. This is ~20 times higher than that consumed by industrial scale gas liquefaction systems, but is practical for a small scale system. This specific power consumption could probably be lowered if the working fluid itself is liquefied. Analysis on wind speed variability and wind speed data synthesis were also performed which suggested presence of multi-fractal nature in wind speed data that represent the temporal variation. A new method developed to generate high sampling frequency wind speed data from available low sampling frequency wind speed data can have contribution in all sectors when there is a need of higher sampling frequency time series data for simulation/study purposes. The liquid nitrogen mass flow rate (kg/s) increased with increase in compressor motor frequency and also when operating at variable motor input frequency. However, the average compressor power consumption also increased compared to average power consumption during operation at standard motor frequency of 60 Hz. This was in a laboratory scale liquefaction system and needs to be tested in the large scale system experimentally. With 1 kg/s of liquefied nitrogen supplied, ~459 kWr of cooling power is available to cool the deep mine air which is at 30-400C. A volumetric flow rate of 0.062 m3/s of liquefied air can provide a cooling power equivalent to that provided by a volumetric flow rate of 4000 m3/s of atmospheric air, which is the requirement of some of the biggest mines in the world. The hydraulic wind turbine as proposed in this work can eliminate the system start-up issues following the calm period, which are typical concerns with the wind energy integrations. This research work has provided the required modeling and simulation results that are crucial in development of the full scale ‘CryoVent’.
Modeling of plasma dynamics during pulsed electron beam ablation of graphite.
(2017-07-26) Ali, Muddassir
Recent advances in the field of plasma nanofabrication suggest that plasma-based technologies may replace many of the conventional chemical and thermal routes in the synthesis of nanomaterials (with at least one dimension below 100 nm) and thin films. In contrast to the conventional processing routes, where only neutral species are involved, a plasma is made up of energetic species including ions, electrons, and excited molecules in addition to neutrals. Due to the highly energetic nature of interactions among these species and with other surfaces (substrates), a plasma allows for the formation of materials at higher rates even though their concentrations might be low as compared with those of neutral species in non-plasma based methods. While the mechanisms of the various interactions in a plasma are undoubtedly complex and require a fundamental understanding, they offer new opportunities for material nanofabrication. Pulsed electron beam ablation (PEBA) has recently emerged as a novel and promising technique for high quality thin films growth. Pulsed electron beam film deposition consists of many physical processes including target material heating, target ablation, plasma plume expansion, and film growth on a substrate. Electron beam ablation is a complex process, which comprises heating, phase change, and removal of a fine fraction from the target surface. Ablation strongly affects the space distribution, composition, mass transfer processes, which in turn has a critical bearing on the structure, stoichiometry and properties of thin films. Plasma plume expansion into an ambient gas is a fundamental issue in PEBA as the quality of thin films deposited onto the substrate depends on the composition, energy and density of particles ejected from the target. A one-dimensional heat conduction model is presented to investigate the heating and ablation of a graphite target upon interaction with a polyenergetic electron beam. The effect of electron beam efficiency, power density, accelerating voltage, and Knudsen layer just above the target surface during ablation are taken into account in the model. Phase transition induced during ablation is considered through the temperature dependent thermodynamic properties of graphite. The temperature distribution, surface receding velocity, melting depth, ablation depth, and ablated mass per unit area are numerically simulated. Upon ablation, plasma expansion, induced by interaction of a nanosecond electron beam pulse (~100 ns) with a graphite target in an argon atmosphere at reduced pressure, was investigated by solving gas-dynamics equations. The spatiotemporal profiles of the temperature, pressure, velocity, and density of the plasma plume are numerically simulated for a beam efficiency of 0.6 and accelerating voltage of 15 kV. Each model is validated by comparing some of the obtained simulation results with experimental data available in the literature.
Design and optimization of a novel top-lit gas-lift bioreactor for industrial CO2 mitigation and microalgae-sourced biodiesel production
(2017-03-24) Seyed Hosseini, Nekoo
Mitigation of CO2 in industrial off-gasses by sparging the gas through photosynthetic microalgae bioreactors is an attractive concept. The goal is for the CO2 to be consumed by the microalgae as a nutrient, which in turn produces lipids suitable for conversion into biodiesel, as well as other value-added bioproducts such as Omega-3 fatty acids and antioxidants. Open systems are considered the most economic outdoor, large-scale cultivation option but have large land space requirements due to their shallow depths (15-35 cm). Consequently, finding sufficient space to locate them close to off-gas sources on industrial sites can be a significant challenge. Shallow depths are also likely to result in low uptake of CO2 and consequently reduced biomass productivity due to short gas residence times in the culture medium. In order to obtain longer gas/liquid transfer times, as well as greater per area productivity, the tanks through which the off-gas is sparged must be as deep as possible. However, to make the tanks deeper and avoid the costs associated with sub-surface artificial lighting, the issue is how to ensure the microalgae receive adequate light exposure. We have, therefore, looked for a novel method for increasing the depth of the tanks through which the off-gas is sparged. To achieve this, we have investigated the use of a gas-lift circulating system in a deep top-lit open bioreactor. In addition to providing CO2, the sparged gas also provides continual vertical circulation of the microalgae to ensure good mixing and an adequate light/dark cycle. Compared to existing shallow open systems, the results obtained showed comparable biomass productivity per unit volume, but importantly around three-times higher biomass productivity per unit area occupied by the bioreactor. The lipid productivity was also increased due to light and hydrodynamic stresses. In order to enhance further light utilization efficiency in the deep cultivation bioreactor, the use of a novel non-energy-consuming light column was also evaluated. The results of using the light column showed a 33% increase in areal biomass productivity and a 16% increase in areal lipid production. The proposed design and developed models can be easily translated into larger scale, onsite production facilities in industrial sectors emitting off-gas. The carbon capturing properties of microalgae can, therefore, help reduce industrial carbon dioxide emissions, whilst at the same time producing biodiesel from the resulting lipids.
Influence of test conditions on post-peak deformation behavior of rock
(2017-04-10) Xu, Yuhang
Understanding the post-peak deformation behavior of rock is important for underground rock engineering. Laboratory property testing is commonly employed to investigate the post-peak deformation behavior. However, the test conditions of laboratory testing, especially the Loading System Stiffness (LSS) of stiff test machines, are usually varied and the influence of this variation on the test results has not been fully elucidated. In addition, studying the influence of test conditions on the post-peak deformation behavior of rock is crucial for interpreting test results and subsequently applying the results to rock engineering design. The goal of this dissertation is to identify how the post-peak deformation behavior of a rock specimen is affected by three major aspects of test conditions––the specimen geometry, the contact conditions, and the LSS. To achieve this goal, an FEM/Explicit tool was employed to carry out numerical experiments, in which the same material property was assumed for the rock specimens and each wanted test condition was isolated for analysis. The well-observed slenderness effect and the recently-observed cross-sectional shape effect on the Uniaxial Compressive Strength (UCS) of rocks were studied. The modeling results suggest that the numerical tool and models are suitable for investigating the problem and the hoop tension theory could be flawed. Next, the cross-sectional shape effect on the post-peak deformation behavior was investigated. The modeling results reveal that although the influence of the cross-sectional shape on the UCS of rocks is small, the cross-sectional shape affects the post-peak deformation behavior considerably. The actual contact condition and the end effect in true triaxial compression tests were simulated while the legitimate intermediate principal stress (2) effect was excluded from the rock material contacts are frictional and the specimen in the 2 loading direction is squat. Thus, existing 3D empirical failure criteria based on previous true triaxial compression test results may overestimate the rock strength. The influence of LSS on the post-peak stress–strain relations of stable rock failure was examined. Key loading components of stiff test machines were considered in the numerical model. The modeling results clarify that LSS affects the post-peak stress–strain curves of rocks even when the failure process is stable. Unless LSS is either perfectly rigid or equivalent to the critical LSS (), the post-peak stress–strain curves obtained under various LSS (with LSS >  ) are varied and all steeper than the one under an ideal loading condition. This dissertation demonstrates the cross-sectional shape effect in the post-peak deformation stage, the long overlooked 2 effect caused by the end effect, and the variation of post-peak stress– strain curves due to the LSS. This dissertation also makes a contribution to examining the hoop tension theory and recognizing the correct choice of cross-sectional shape for test specimens, offers insights into improving 3D empirical failure criteria and true triaxial test settings, and suggests new requirements for developing stiff test machines in the future.

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