Thesis (DTech (Education))--Cape Peninsula University of Technology, 2009 / The phenomena of multi - grade schools has been absent both in educational policy making, educator training and only represented in a few local educational curriculum research projects. However, the practice of multi-grade is common in South Africa and especially in rural and farming South Africa. Our National Curriculum Statements implies that all schools are the same. This study addresses this anomaly. Farm schools, which started as a political means of cheap labour (Act 47 of 1953) presented a further complication to the ministry: public schools on private property govern by section 14 contract failed farm education (Forgotten Schools, 2004; Ministerial report on rural education, 2005; Commission on Human Rights, 2006). The political and ideological shift from People's Education, which, at first envision human rights in line with international treaties such Education For All, Convention on the right of the child, Africa Charter on the Rights of the Child to Human Capital Development has marginalize the farm and rural learner. Curriculum changes since Curriculum 2005 accepted the same political and economic vision. The first world technical National Curriculum Statements mismatch farm education as systemic results since 2004 has shown. The government’s deficit view and national curriculum influence farm and rural teaching and learning negatively. This study focuses on curriculum delivery (intended I implemented) planning. How the educator adapted the curriculum to suit the needs of third world farm learner, its multi-grade context and the ideology of the hegemony. The qualitative paradigm will be that of the critical theory and grounded theory methodology with the goal of uncovering the educators' views and practice. This has been done by holding interviews with various foundation phase educators and looking at the seating arrangements and planning. The sample was from the Breede River District. A focus group of nineteen ACE students with 312 collective years experience has been involved in the coding and analysing. Current practice and planning have been juxtaposed with international multi-grade practice. The research questions were aimed at uncovering how rural and farm educators plan for their multi-grade classes when faces with a national mono-grade curriculum. Various research methodologies were used.

To prevent the global surface temperature from increasing past the 2 oC target, it is necessary to address CO2 emissions from small point sources. Within Canada’s heavy oil industry, SAGD facilities use natural gas combustion to produce the large amounts of steam required for the process, which produces approximately 0.5-2 Mtonnes of CO2 per annum. A suitable technology for CO2 mitigation from a SAGD facility is Pressurized Chemical Looping Combustion. PCLC is an oxy-combustion, carbon capture technology with a relatively low predicted energy penalty of 3-4%. The process requires a dual, interconnected fluidized bed reactor system with circulating solids. Natural gas is converted in the fuel reactor via a solid metal oxide, which is then circulated to the air reactor for reoxidation with air. As the cost of air compression is significant, the economical feasibility of the process is reliant on air reactor performance. The objective of this study is to investigate the oxidation reaction and derive a kinetic model for reactor design and performance assessment purposes. Ilmenite ore was chosen as the metal oxide, as it is low cost and has desirable oxygen transport properties for PCLC. Pressurized TGA tests were conducted to study the effects of oxygen concentration, temperature and pressure on the rate of the oxidation reaction. The total pressure was varied from 1-16 bara at 900 oC with air. The oxygen concentration was varied from 2.5-21 vol%, and the temperature from 800-1000 oC at 8 bar. Temperatures below 850 oC resulted in segregation of the Fe and Ti phase in the ilmenite ore, leading to a reduction in the overall oxygen carrying capacity. Crack formation was observed at higher oxygen partial pressures, resulting in increased surface area for reaction and a fast reaction rate. At lower oxygen partial pressures, a solid-state diffusion controlled regime was observed due to the absence of fissures. A dual mechanistic oxidation kinetic model was derived at 8 bar, with 2nd order random nucleation dominating at lower conversions, and Jander’s solid state diffusion model dominating at higher conversions. The transition from the nucleation and growth to the diffusion-controlled portion occurred at higher conversions with higher oxygen partial pressure. The activation energy was 16.6 kJ/mol and 48.7 kJ/mol while the order of reaction with respect to oxygen was 0.3 and 1.3 for respectively the nucleation and growth, and diffusion-controlled regimes. A preliminary air reactor model is constructed as a turbulent bed. The turbulent bed is modelled as an axial dispersion reactor for a basic performance assessment.

Detailed sensitivity numerical studies have shown that the mesh cell-size may have a drastic effect on the modelling of circulating fluidized bed with small particles. Typically, the cell-size must be of the order of few particle diameters to predict accurately the dynamical behaviour of a fluidized bed. Hence, the Euler-Euler numerical simulations of industrial processes are generally performed with grids too coarse to allow the prediction of the local segregation effects. Appropriate modelling, which takes into account the influence of unresolved structures, have been already proposed for monodisperse simulations. In this work, the influence of unresolved structures on a binary mixture of particles is investigated and models are proposed to account for those effect on bidisperse simulations of bidisperse gas-solid fluidized bed. To achieve this goal, Euler-Euler reference simulations are performed with grid refinement up to reach a mesh independent solution. Such kind of numerical simulation is very expensive and is restricted to very simple configurations. In this work, the configuration consists of a 3D periodical circulating fluidized bed, that could represent the established zone of an industrial circulating fluidized bed. In parallel, a filtered approach is developed where the unknown terms, called sub-grid contributions, appear. They correspond to the difference between filtered terms, which are calculated with the reference results then filtered, and resolved contributions, calculated with the filtered fields. Then spatial filters can be applied to reference simulation results to measure each sub-grid contribution appearing in the theoretical filtered approach. A budget analysis is carried out to understand and model the sub-grid term. The analysis of the filtered momentum equation shows that the resolved fluid-particle drag and inter-particle collision are overestimating the momentum transfer effects. The analysis of the budget of the filtered random kinetic energy shows that the resolved production by the mean shear and by the mean particle relative motion are underestimating the filtered ones. Functional models are proposed for the subgrid contributions of the drag and the inter-particle collision.

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Traditional chemical looping technologies utilize solid oxygen carriers and has some disadvantages, especially when solid fuels like coal are used. In this work, a novel chemical looping process using gaseous metal oxide as oxygen carrier was proposed. The reaction of activated charcoal with gas-phase MoO3 was studied for the first time. The experiments were conducted isothermally at different temperatures in a fixed-bed reactor. The apparent activation energy of the reaction was calculated and suitable kinetic models were determined. The results and analysis showed that the proposed concept has potential in both coal chemical looping combustion and gasification process. To further investigate the mechanism of carbon oxidation by gas-phase MoO3, the adsorption of a gaseous (MoO3)3 cluster on a graphene ribbon and subsequent generation of COx was studied by density functional theory (DFT) method and compared with experimental results. The (MoO3)n -graphene complexes show interesting magnetic properties and potentials for nanodevices. A comprehensive analysis of plausible reaction mechanisms of CO and CO2 generation was conducted. Multiple routes to CO and CO2 formation were identified. The (MoO3)3 cluster shows negative catalytic effect for CO formation but does not increase the energy barrier for CO2 formation, indicating CO2 is the primary product. Mechanism of the homogenous MoO3 - CO reaction was studied and showed relatively low energy barriers. The DFT result accounts for key experimental observations of activation energy and product selectivity. The combined theoretical and experimental approach contributes to the understanding of the mechanism of reactions between carbon and metal oxide clusters. To gain a better understanding of the MoO2 oxidation process, the adsorption and dissociation of O2 on MoO2 surface were studied by DFT method. The results show that O2 molecules prefer to be adsorbed on the five-coordinated Mo top sites. Density of states analysis shows strong hybridization of Mo 4d orbitals and O 2p orbitals in the Mo-O bond. Clean MoO2 slab and slabs with O2 adsorption are metallic conductors, while the surface with high O atom coverage is reconstructed and becomes a semiconductor. Surface Mo atoms without adsorbed O or O2 are spin-polarized. The oxygen adsorption shows ability to reduce the spin of surface Mo atoms. The adsorption energy of O2 and O atoms decreases as coverage increases. The transition states of O2 dissociation were located. The energy barriers for O2 dissociation on five-coordinated and four-coordinated Mo top sites are 0.227 eV and 0.281 eV, respectively.

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To achieve net-zero emissions by the year 2050, carbon capture, utilization and storage technologies must be implemented to decarbonize sectors with hard-to-abate emissions. Pressurized chemical looping (PCL) with a novel reactor design called a plug flow with internal recirculation (PFIR) fluidized bed reactor is proposed as an attractive carbon capture technology to decarbonize small- and medium-scale emitters. The objective of this work was to examine solid circulation rate, gas leakage between reactors, and purge gas fate in a cold flow chemical looping facility. These parameters were used to better understand the PFIR reactor and will be used to validate a computational particle fluid dynamic (CPFD) model of the PFIR reactor to inform the reactor operation and design for a hot flow PCL pilot plant. An energy balance across the fuel reactor was used to determine the solid circulation rate of the bed material, while helium and argon tracer gases were used to determine the amount of gas leaking between reactor sections and the fate of the purge gas, respectively. Statistical analyses were completed to determine the statistical significance of the data. At the base case condition, the solid circulation rate was 3000 kg/h. Approximately 10% of the fluidizing gas that entered the air reactor moved to the fuel reactor indicating that, with reacting flow, there will be nitrogen infiltrating the fuel reactor, decreasing the purity of the carbon dioxide effluent stream. Furthermore, approximately 31% of the fluidizing gas entering the fuel reactor moved to the air reactor, indicating that, with reacting flow, there will be natural gas leaking into the air reactor, which will increase carbon dioxide emissions. Finally, over half of the purge gases move to the adjacent reactor, which helps prevent gas leakage between reactor sections. The effect of static bed height, weir opening height and purge configuration on solid circulation rate, gas leakage and purge fate were investigated. The bed height has a small effect on the solid circulation rate and no effect of gas leakage, over the range of bed heights tested. Furthermore, increasing the weir opening height increases both solid circulation rate and gas leakage until the top of the circulation zone is reached. After this point, there is no change in either solid circulation rate or gas leakage. In terms of purge configuration, there appears to be no benefit for having two purge rows. Either one purge row or having a row of blanked tuyeres appear to be optimal as they decrease gas leakage, while having little effect on solid circulation rate. At the jet velocity tested, the vertical purge configuration prevented the solids from circulating, so it is not recommended for this purge configuration to be used in a PFIR reactor without further testing of different jet velocities. Across all configurations, it was shown that as more purge gas moves into the adjacent reactor section, less gas leakage between reactor sections occurs. It iii was also determined that the primary method of gas movement between the reactor sections is likely via bubbles and/or jets. The next step is to complete the validation of CPFD model of the PFIR reactor using the data presented herein. Additional conditions can also be run in the cold flow chemical looping pilot facility to fill in any gaps that are found during the CPFD model validation, or to fill in research gaps in better understanding the PFIR reactor.