Human capital is the only resource within an organisation that can learn. Developing high levels of competence in employees is one of the most challenging issues in organisations. Off–the–Job training programs either miss the mark or are too far away from the performance setting to have the desired impact on employee competence. Studies have shown that unstructured On–the–Job Training (OJT) leads to increased error rate, lower productivity and decreased training efficiency, compared to structured On–the–Job Training(S–OJT). The proven efficiency and effectiveness of S–OJT make it especially suitable to meet this challenge. Though S–OJT has been around for a while there has not been a proper integration of technology into the process. Every training approach, including S–OJT, is merely a means to an end, not an end in itself. The use of S–OJT helps to develop consistent appropriate levels of employee competence. When employees have these competencies e.g. better knowledge of the production processes, they can increase productivity, complete projects on time, lower defect rates, or achieve other outcomes of importance. These are the outcomes that matter to the organisation and the effectiveness of S–OJT should be judged from this perspective. Researchers have consistently found that one way to improve learners' success is to increase the frequency of exams. Classes meet for a set number of times. An instructor's decision to give more exams typically means that students have less time for learning activities during class meetings. How then can one have the best of both worlds, increasing the number of assessments and at the same time having enough time for learning activities? This can only be accomplished by integrating computer–based assessment into S–OJT programs. Computer–based testing and training can provide flexibility, instant feedback, an individualised assessment and eventually lower costs than traditional written examinations. Computerised results create opportunities for teaching and assessment to be integrated more than ever before and allow for retesting students, measuring growth and linking assessment to instruction. This research aims to evaluate the effectiveness of integrating computer–based testing and training into S–OJT programs using the Air Separation unit of Sasol Synfuels as a case study. The null hypothesis is used to investigate the draw backs of OJT and S–OJT programs. A framework is also developed for the effective integration of CBT into S–OJT programs. / Thesis (M.Ing. (Development and Management))--North-West University, Potchefstroom Campus, 2011.

Human capital is the only resource within an organisation that can learn. Developing high levels of competence in employees is one of the most challenging issues in organisations. Off–the–Job training programs either miss the mark or are too far away from the performance setting to have the desired impact on employee competence. Studies have shown that unstructured On–the–Job Training (OJT) leads to increased error rate, lower productivity and decreased training efficiency, compared to structured On–the–Job Training(S–OJT). The proven efficiency and effectiveness of S–OJT make it especially suitable to meet this challenge. Though S–OJT has been around for a while there has not been a proper integration of technology into the process. Every training approach, including S–OJT, is merely a means to an end, not an end in itself. The use of S–OJT helps to develop consistent appropriate levels of employee competence. When employees have these competencies e.g. better knowledge of the production processes, they can increase productivity, complete projects on time, lower defect rates, or achieve other outcomes of importance. These are the outcomes that matter to the organisation and the effectiveness of S–OJT should be judged from this perspective. Researchers have consistently found that one way to improve learners' success is to increase the frequency of exams. Classes meet for a set number of times. An instructor's decision to give more exams typically means that students have less time for learning activities during class meetings. How then can one have the best of both worlds, increasing the number of assessments and at the same time having enough time for learning activities? This can only be accomplished by integrating computer–based assessment into S–OJT programs. Computer–based testing and training can provide flexibility, instant feedback, an individualised assessment and eventually lower costs than traditional written examinations. Computerised results create opportunities for teaching and assessment to be integrated more than ever before and allow for retesting students, measuring growth and linking assessment to instruction. This research aims to evaluate the effectiveness of integrating computer–based testing and training into S–OJT programs using the Air Separation unit of Sasol Synfuels as a case study. The null hypothesis is used to investigate the draw backs of OJT and S–OJT programs. A framework is also developed for the effective integration of CBT into S–OJT programs. / Thesis (M.Ing. (Development and Management))--North-West University, Potchefstroom Campus, 2011.

Support for this work from Praxair; the McMaster Advanced Control Consortium; and the Natural Sciences and Engineering Research Council of Canada (NSERC), Grant CRDPJ 445717, is gratefully acknowledged. / In the air separation industry, cryogenic distillation is the dominant technology for separating large quantities of air into individual high purity component products. Due to the complexity of the process, in addition to significant energy input, air separation units (ASUs) also have high degrees of material and thermal integration and low process agility. As markets become more competitive and dynamic, especially after electricity market deregulation, ASUs can no longer practice mostly stationary operations, and are in need for design and control strategies to achieve high adaptability. In this study, we address such issues through a dynamic optimization framework. The use of rigorous dynamic models is important for developing economically beneficial designs and operating practices. The first part of this study focuses on the modeling aspect. For the column section of the plant, a full-order stage-wise model and a collocation based reduced order model are proposed. Model size, simulation time and predication accuracy are compared. For the primary heat exchanger, a novel moving boundary model is derived to handle the phase change in such a multi-stream heat exchanger. Simulation results demonstrate the capability of the proposed model in tracking the boundary points of the phase change occurrence, as well as the potential pinch point, along the length of the heat exchanger. The second part of the study addresses the operation aspects of ASUs through conducting dynamic optimization studies with collocation based dynamic models. We first performed a comprehensive analysis for a storage-then-utilization strategy on a nitrogen plant, following a two-tier multi-period formulation. As the parameter varies with time, the plant collects liquid, either directly from liquid product or by liquefaction of overproduced gas product, and then redistributes it for meeting gas product demand or as additional reflux. Effects of electricity price and demand profiles, additional operation costs, as well as product specifications are explored. Then we investigated the economic incentive for employing preemptive actions on a super-staged argon system, which allows the plant to take actions before external changes arrive. In the evaluation, changes are in the gas oxygen product demand. During the preemptive period, the plant takes either a single set or multiple sets of control actions. In the demand increase case, operation degrees of freedom are introduced to or removed from the set of decision variables. The demand decrease scenarios are explored with an under-supplied or saturated liquid oxygen market. / Dissertation / Doctor of Philosophy (PhD)

The objective of this thesis is to provide an extensive description of the correlations in some of the most crucial sub-processes for hard coal fired IGCC with carbon capture (CC-IGCC). For this purpose, process simulation models are developed for four industrial gasification processes, the CO-shift cycle, the acid gas removal unit, the sulfur recovery process, the gas turbine, the water-/steam cycle and the air separation unit (ASU). Process simulations clarify the influence of certain boundary conditions on plant operation, performance and economics. Based on that, a comparative benchmark of CC-IGCC concepts is conducted. Furthermore, the influence of integration between the gas turbine and the ASU is analyzed in detail. The generated findings are used to develop an advanced plant configuration with improved economics. Nevertheless, IGCC power plants with carbon capture are not found to be an economically efficient power generation technology at present day boundary conditions.

Cette thèse porte sur la modélisation, pour le contrôle, des profils de compositions dans les colonnes de distillation cryogénique. Nous obtenons un modèle non-linéaire de convection-diffusion par réduction d'un modèle d'équations-bilans singulièrement perturbé. Du point de vue de l'automatique, nous nous intéressons à la stabilité des profils de compositions résultants, ainsi qu'à leur observabilité. Du point de vue du procédé, la nouvauté de notre modèle réside dans la prise en compte d'une efficacité de garnissage dépendant des conditions d'opération de la colonne. Le modèle est validé par des comparaisons avec des données de fonctionnement dynamique issues d'une unité de séparation réelle, pour la séparation d'un mélange binaire. Sur le cas plus complexe d'une cascade de colonnes séparant un mélange ternaire, le modèle montre une grande sensibilité aux erreurs d'estimation des taux de reflux. Des résultats adaptés du champ de la chromatographie nous permettent de relier cette sensibilité à des erreurs d'estimation des vitesses d'ondes de compositions cohérentes. En parallèle, nous proposons et testons également un modèle de fonctions de transfert simple (fondé sur des gains statiques et des retards purs uniquement) pour les petites dynamiques de compositions, qui dépend explicitement de valeurs mesurables ou observables sur le procédé / This thesis addresses the problem of modeling the composition profiles dynamics inside cryogenic distillation columns, for control applications. We obtain a non-linear convection-diffusion model from the reduction of a singularly perturbed mass-balances model. In the control theory framework, we consider the stability of the resulting composition profiles and their observability. From the process viewpoint, we express the novelty of our model in terms of operating-conditions dependent packing efficiency. The model is validated against real dynamic plant data for a binary separation case. On a more complex, ternary separation columns cascade, the model shows highly sensitive to reflux rate estimation errors. Result adapted from the field of chromatography allows us to interpret this sensitivity in terms of erroneous coherent composition waves speeds. In parallel, we also propose and test a simple transfer functions model (based on static gains and pure delays only) for small composition dynamics, which explicitly depends on measurable or observable process data.

The objective of this thesis is to provide an extensive description of the correlations in some of the most crucial sub-processes for hard coal fired IGCC with carbon capture (CC-IGCC). For this purpose, process simulation models are developed for four industrial gasification processes, the CO-shift cycle, the acid gas removal unit, the sulfur recovery process, the gas turbine, the water-/steam cycle and the air separation unit (ASU). Process simulations clarify the influence of certain boundary conditions on plant operation, performance and economics. Based on that, a comparative benchmark of CC-IGCC concepts is conducted. Furthermore, the influence of integration between the gas turbine and the ASU is analyzed in detail. The generated findings are used to develop an advanced plant configuration with improved economics. Nevertheless, IGCC power plants with carbon capture are not found to be an economically efficient power generation technology at present day boundary conditions.