Slot-rectangular spouted beds, with rectangular cross-section and slotted gas inlets, have been proposed as a solution to overcoming scale-up difficulties with conventional axisymmetric spouted beds. They can be utilized in gas/particle processes such as drying of coarse particles and coating of tablets. However, application of this spouted bed was limited because of instability and insufficient hydrodynamic studies. The present work is therefore aimed at the study of hydrodynamics, stability and scale-up of slot-rectangular spouted beds. The hydrodynamic study was carried out in four slot-rectangular columns of various width-to-thickness ratios combined with various slot configurations, particles of different properties and a range of operating conditions. Hydrodynamics of slot-rectangular spouted beds showed major similarity with conventional spouted beds. However, equations and mechanistic models adopted from conventional axisymmetric spouted beds generally failed to provide good predictions for the three-dimensional slot-rectangular geometry. New empirical correlations were derived for the minimum spouting velocity and maximum pressure drop for different slot configurations. Slot-rectangular spouted beds also showed more flow regimes than conventional spouted beds. Nine flow regimes, as well as unstable conditions, were identified based on frequency and statistical analysis of pressure fluctuations. Slot geometrical configuration was found to be the main factor affecting the stability of slot-rectangular spouted beds. A comprehensive hydrodynamic study on the effect of slot configuration was therefore carried out. Slots of smaller length-to-width ratio, smaller length and greater depth were found to provide greater stability. Stable criteria for the slot configuration were found consistent with the conventional axisymmetric spouted beds with extra limitation on slot length-to-width ratio and slot depth. Local distributions of pressure, particle velocity and voidage, as well as spout shape and particle circulating flux, were compared for different slot configurations. Higher slot length-to-width ratios lead to slightly higher particle circulation rates. A previously proposed scale-up method involving multiple chambers was tested in the present work using multiple slots. Instability caused by the merging of multiple spouts and asymmetric flow was successfully prevented by suspending vertical partitions between the fountains. Some criteria and guidelines were also proposed for scale-up using multiple chambers. / Applied Science, Faculty of / Chemical and Biological Engineering, Department of / Graduate

The Student-Centered Active Learning Environment for Undergraduate Programs (SCALE-UP) method incorporates active learning pedagogies into space designed to facilitate effective active learning. Methods predominately used to demonstrate the effectiveness of active learning in STEM fields do not generally account for differences in student characteristics; furthermore, there is a lack of data sources that measure student-centered educational practices. This study examined the impact of SCALE-UP on student achievement in introductory biology, as evidenced by course grades. A regression framework was used to account for student characteristics. Course syllabi, classroom observation data, and an instructor interview were examined to gain deeper understanding of teaching practices across classes being compared. Findings indicate the SCALE-UP classroom did not directly impact biology course grades; however, it did impact the nature of active learning techniques used during the course. Implications for practice and future research were discussed.

The main goal of this master’s thesis is to investigate the drawn down of floating particles in mechanically stirred vessels. The first part of the thesis summarizes necessary theory to cope with defined objectives of the thesis. The literature review of mixing reactors with floating particles can be found in this part of the work as well. The second part of the master’s thesis includes the preparation of the stirred tanks CFD model, simulation and comparing of experimental data from literature, as well.

Graph-structured data can be found in nearly every aspect of today's world, be it road networks, social networks or the internet itself. From a processing perspective, finding comprehensive patterns in graph-structured data is a core processing primitive in a variety of applications, such as fraud detection, biological engineering or social graph analytics. On the hardware side, multiprocessor systems, that consist of multiple processors in a single scale-up server, are the next important wave on top of multi-core systems. In particular, symmetric multiprocessor systems (SMP) are characterized by the fact, that each processor has the same architecture, e.g. every processor is a multi-core and all multiprocessors share a common and huge main memory space. Moreover, large SMPs will feature a non-uniform memory access (NUMA), whose impact on the design of efficient data processing concepts should not be neglected. The efficient usage of SMP systems, that still increase in size, is an interesting and ongoing research topic. Current state-of-the-art architectural design principles provide different and in parts disjunct suggestions on which data should be partitioned and or how intra-process communication should be realized. In this thesis, we propose a new synthesis of four of the most well-known principles Shared Everything, Partition Serial Execution, Data Oriented Architecture and Delegation, to create the NORAD architecture, which stands for NUMA-aware DORA with Delegation. We built our research prototype called NeMeSys on top of the NORAD architecture to fully exploit the provided hardware capacities of SMPs for graph pattern matching. Being an in-memory engine, NeMeSys allows for online data ingestion as well as online query generation and processing through a terminal based user interface. Storing a graph on a NUMA system inherently requires data partitioning to cope with the mentioned NUMA effect. Hence, we need to dissect the graph into a disjunct set of partitions, which can then be stored on the individual memory domains. This thesis analyzes the capabilites of the NORAD architecture, to perform scalable graph pattern matching on SMP systems. To increase the systems performance, we further develop, integrate and evaluate suitable optimization techniques. That is, we investigate the influence of the inherent data partitioning, the interplay of messaging with and without sufficient locality information and the actual partition placement on any NUMA socket in the system. To underline the applicability of our approach, we evaluate NeMeSys against synthetic datasets and perform an end-to-end evaluation of the whole system stack on the real world knowledge graph of Wikidata.

The future of fuels will most probably be a mixture of different fuels, called drop-in fuels. It is already known that these drop-in fuels will lead to solubility issues, with creation of deposit on crucial fuel system parts, due to the formation of soft particles. The fuel system of the future should be robust against any type of soft particles. Today, there is no scaled up test fluid existing for testing full scale fuel systems. The objective of this thesis was to develop a scaled up test fluid which is a key element to the development of a test method to enhance the fuel system robustness against soft particles. A test fluid was achieved by a concentrate of calcium soap diluted two thousand times to reach a volume of 1000 litres with a concentration of 1,4 ppm. The concentration was measured by gas chromatography mass spectroscopy method following a derivatisation as sample preparation. The formation of the concentrate was established by changing the type of fuel, the level of aging, the amount of calcium and other counterions and eventually by addition of third elements. The concentrate was made of aged B100, calcium oxide powder and water. The test fluid was made by diluting the concentrate with fresh B7 and a protocol to characterise the stability of this test fluid was developed. This test fluid was tested under real condition in a filter rig giving homogeneous concentration all along the experiment, which confirmed the stability of the test fluid.

The need for a safe and sustainable chemical industry has called for the development of emerging technologies with improved environmental performance. In this study, an emerging electrochemical hydrogenation process over Ni foam is being developed at the laboratory scale with an expectation of less environmental impacts than a conventional palladium on carbon hydrogenation process. To understand better the potential environmental performance of the process at the matured scale, a prospective life cycle assessment was conducted to identify environmental hotspots for early process improvement. There is no standardised method for prospective life cycle assessment, hence a methodological recommendation in conducting a prospective LCA was proposed through a literature review.  The proposed methodology consists of three steps which are a pre-inventory stage, an inventory stage, and a post-inventory stage. These steps have been connected to the ISO 14044 standard methodology for conducting an LCA where the pre-inventory stage relates to the goal and scope definition, the inventory stage to inventory analysis, and the post-inventory connected to both the inventory analysis, impact assessment, and interpretation stages of the ISO methodology. The proposed methodology was applied to the electrochemical hydrogenation process over nickel foam cathode where a three-case scenario (lab, worst- and best-case scenarios) was investigated to identify hotspots for early process improvement. The theoretical upscaled process had a better environmental performance compared to the lab process. The identified hotspots in the upscaled process (worst-case) include electricity process, evaporation process, and solvent recycling process for ecotoxicity (freshwater), human toxicity (cancer), human toxicity (non-cancer), climate change and resource use (minerals and metals) impact categories. The best-case scenario had its identified hotspots in the electricity process, solvent recycling process, and distillation process. This shows the importance of circularity, recycling, and lean manufacturing to the pillars of sustainability. Reducing resource consumption per unit product while increasing the recycling efficiency of process waste will be imperative towards ensuring a green chemical industry. Based on the results, a reduction of electricity demand for the process, utilisation of an alternative less energy-consuming processes, or cleaner energy sourcing could further improve the potential environmental performance of the process. Based on the quality of the data used, it is recommended that the outcome of the study be cautiously interpreted.

The objective of this study was to evaluate the effect of two pedagogical models used in general education science on non-majors' science teaching self-efficacy. Science teaching self-efficacy can be influenced by inquiry and cooperative learning, through cognitive mechanisms described by Bandura (1997). The Student Centered Activities for Large Enrollment Undergraduate Programs (SCALE-UP) model of inquiry and cooperative learning incorporates cooperative learning and inquiry-guided learning in large enrollment combined lecture-laboratory classes (Oliver-Hoyo & Beichner, 2004). SCALE-UP was adopted by a small but rapidly growing public university in the southeastern United States in three undergraduate, general education science courses for non-science majors in the Fall 2006 and Spring 2007 semesters. Students in these courses were compared with students in three other general education science courses for non-science majors taught with the standard teaching model at the host university. The standard model combines lecture and laboratory in the same course, with smaller enrollments and utilizes cooperative learning. Science teaching self-efficacy was measured using the Science Teaching Efficacy Belief Instrument - B (STEBI-B; Bleicher, 2004). A science teaching self-efficacy score was computed from the Personal Science Teaching Efficacy (PTSE) factor of the instrument. Using non-parametric statistics, no significant difference was found between teaching models, between genders, within models, among instructors, or among courses. The number of previous science courses was significantly correlated with PTSE score. Student responses to open-ended questions indicated that students felt the larger enrollment in the SCALE-UP room reduced individual teacher attention but that the large round SCALE-UP tables promoted group interaction. Students responded positively to cooperative and hands-on activities, and would encourage inclusion of more such activities in all of the courses. The large enrollment SCALE-UP model as implemented at the host university did not increase science teaching self-efficacy of non-science majors, as hypothesized. This was likely due to limited modification of standard cooperative activities according to the inquiry-guided SCALE-UP model. It was also found that larger SCALE-UP enrollments did not decrease science teaching self-efficacy when standard cooperative activities were used in the larger class.

Polymer extrusion is an energy intensive process whereby the simultaneous action of viscous shear and thermal conduction are used to convert solid polymer to a melt which can be formed into a shape. To optimise efficiency, a homogeneous melt is required with minimum consumption of process energy. In this work, in-process monitoring techniques have been used to characterise the thermal dynamics of the single screw extrusion process with real-time quantification of energy consumption. Thermocouple grid sensors were used to measure radial melt temperatures across the melt flow at the entrance to the extruder die. Moreover, an infrared sensor flush mounted at the end of the extruder barrel was used to measure non-invasive melt temperature profiles across the width of the screw channel in the metering section of the extruder screw. Both techniques were found to provide useful information concerning the thermal dynamics of the extrusion process; in particular this application of infrared thermometry could prove useful for industrial extrusion process monitoring applications. Extruder screw geometry and extrusion variables should ideally be tailored to suit the properties of individual polymers but in practise this is rarely achieved due the lack of understanding. Here, LDPE, LLDPE, three grades of HDPE, PS, PP and PET were extruded using three geometries of extruder screws at several set temperatures and screw rotation speeds. Extrusion data showed that polymer rheology had a significant effect on the thermal efficiency on the extrusion process. In particular, melt viscosity was found to have a significant effect on specific energy consumption and thermal homogeneity of the melt. Extruder screw geometry, set extrusion temperature and screw rotation speed were also found to have a direct effect on energy consumption and melt consistency. Single flighted extruder screws exhibited poorer temperature homogeneity and larger fluctuations than a barrier flighted screw with a spiral mixer. These results highlighted the importance of careful selection of processing conditions and extruder screw geometry on melt homogeneity and process efficiency. Extruder scale was found to have a significant influence on thermal characteristics due to changes in surface area of the screw, barrel and heaters which consequently affect the effectiveness of the melting process and extrusion process energy demand. In this thesis, the thermal and energy characteristics of two single screw extruders were compared to examine the effect of extruder scale and processing conditions on measured melt temperature and energy consumption. Extrusion thermal dynamics were shown to be highly dependent upon extruder scale whilst specific energy consumption compared more favourably, enabling prediction of a process window from lab to industrial scale within which energy efficiency can be optimised. Overall, this detailed experimental study has helped to improve understanding of the single screw extrusion process, in terms of thermal stability and energy consumption. It is hoped that the findings will allow those working in this field to make more informed decisions regarding set conditions, screw geometry and extruder scale, in order to improve the efficiency of the extrusion process. / Engineering and Physical Sciences Research Council

Process scale-up studies are, generally, non-linear. This basically means that it is not possible to take a chemical process in the laboratory and bring it to a pilot or production plant by simply increasing the quantities of chemicals and the equipment size proportionally. There are many physico-chemical processes involved (such as reaction kinetics, fluid mechanics and thermodynamics), plus over the years a myriad of different equipment (stirrers, baffles, jackets...) have been developed with different geometrical and performance characteristics. Therefore, scale-up studies involve engineering issues, economic considerations, and risks assessment to reduce them to acceptable levels for the successful commercial scale implementation. Mixing and heat transfer assessments are often required when scaling a process, troubleshooting poor performance or transferring from one plant to another. This is because the rates of these physico-chemical processes are a function of the details of the equipment set-up and operating conditions, so they can vary widely from one vessel to another. Due to this series of drawbacks and the large number of parameters involved, there is the increasing interest to make use of scientific approaches in the early stages of process development, both modelling and simulation tools along with experimentation to try to predict the behaviour of chemical processes on a larger scale and, consequently, reduce costs and efforts from the beginning. This project was aimed at implementing a method to characterize production equipment and calculate its heat transfer coefficient experimentally from a thermal test. Both the created database, which contains information of about 70 reactors, and the heat transfer coefficient values are then used in different case studies with the objective of predicting the behaviour of the chemical processes examined at different scales: laboratory, pilot and production. The scale-up parameters calculation is detailed for each project with emphasis on the results and conclusions regarding the mixing and heat transfer performances.

Thesis (MScEng (Process Engineering))--University of Stellenbosch, 2010. / Thesis submitted in partial fulfilment of the requirements for the Degree of MASTER OF SCIENCE IN ENGINEERING (MINERAL PROCESSING) in the Department of Process Engineering at the University of Stellenbosch / ENGLISH ABSTRACT: The use of dimensional analysis to scale-up mechanically agitated flotation processes and to identify deficiencies in froth flotation plants was explored. The full range of operating variables was considered, such as particle size distribution, reagent suite, conditioning time, retention time, machine geometry, aeration, solids suspension, power requirements and turbulence. Dimensional analysis offers a methodology to combine variables into dimensionless groups to guide the scale-up process based on the notion of similarity. Ten dimensionless groups were developed and combined with metallurgical variables, such as liberation, reagents dosage and flow diagrams to produce a scale-up and evaluation tool, applicable to any mechanically agitated flotation process. In many hydrodynamic studies, the researchers considered hydrodynamic variables based on rotor diameter. In this case the hydrodynamic variables based on rotor diameter represent mechanism “ability”, while parameters based on cell diameter are considered “requirement”. Dimensionless groups have also been applied to the definition of basic parameters of the kinetic constant, such as floatability, bubble surface area flux and froth recovery factor. It also showed that the bubble surface area flux has a maximum with increased aeration, where similar models do not show this dependence. Analysis by computational fluid dynamics and Perspex modelling revealed valuable insight into the inner working of the Wemco flotation machine, such as air dispersion, turbulence levels, separation zones and solids concentration. Design changes to the rotor, disperser, hood and geometrical lay-out produced a marked improvement in flotation conditions. It also supported certain dimensionless numbers measured in full scale plants. Case studies confirmed that almost all flotation plants, irrespective of the minerals floated, suffer from the same deficiencies. Dimensional similitude offers a unique tool to identify these deficiencies and to predict the effect of recommended improvements. In almost every case where the fundamental requirement of similarity was applied, an improvement in performance was observed. Finally a new algorithm is proposed for the scale-up of flotation plants and the application is demonstrated in the design and testing of a pilot plant. / AFRIKAANSE OPSOMMING: Die gebruik van dimensionele analise in die opskaal van flottasieprosesse en die identifisering van flottasieaanlegprobleme is ondersoek. Die volle bereik van bedryfsveranderlikes is ondersoek, soos partikelgrootte, kondisioneringstyd, retensietyd, geometrie, lugvloei, suspensie van vastestowe, turbulensie en drywingsvereistes. Dimensielose analise is die proses waardeur veranderlikes deur wiskundige manipulasie gekombineer word in dimensielose groepe. Tien dimensielose groepe is ontwikkel en is tesame met metallurgiese veranderlikes soos vrystelling, reagensdosering en vloeidiagramme gekombineer om gebruik te word om gelykvormigheid te bewerkstellig. Hierdie proses is van toepassing op enige flottasieproses gebaseer op meganies geagiteerde toerusting. Dimensielose groepe is ook gebruik in die definisie en kwantifisering van turbulensie, agitasie, geometrie, suspensie van vastestowe, verspreiding van lug en drywingsvereistes. Daarbenewens is die groepe gebruik in die definisie van die basiese veranderlikes van die kinetiese konstante soos lugborreloppervlakvloed, suspensie, en herwinning in die skuimfase. Die groepe is ook gebruik in die bewys dat die lugborreloppervlakvloed ´n maksimum het met toename in lugvloei. In baie gevalle word hidrodinamiese veranderlikes uitgedruk in terme van die rotordiameter en in hierdie studie word dit beskou as meganisme “vermoë”. Die hidrodinamiese veranderlikes gebaseer op sel-diameter word beskou as “behoefte”. Berekeningsvloeidinamika en Perspex modellering het waardevolle insig verskaf in die binne-werking van die Wemco flottasiemasjien soos lugverspreiding, turbulensie en partikelkonsentrasie en is ook gebruik om sekere dimensielose getalle wat in volskaalse aanlegte gemeet is, te verifieer. Gevallestudies het bevestig dat feitlik alle flottasieaanlegte, ongeag die soort mineraal, gebuk gaan onder dieselfde afwykings. Dimensionele analise bied ‘n eenvoudige benadering om hierdie afwykings te identifiseer en om die effek van veranderings te voorspel. In alle gevalle waar die beginsels van gelykvormigheid slaafs gevolg is, het n merkbare verbetering in prestasie voorgekom. Ten slotte is ´n nuwe opskaleringsalgoritme ontwikkel en is die toepassing daarvan gedemonstreer deur die ontwerp en toets van ´n loodsaanleg, gebaseer op die Wemco geometrie.