Made available in DSpace on 2014-10-09T12:49:28Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:01:16Z (GMT). No. of bitstreams: 0 / Dissertacao (Mestrado) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares, IPEN/CNEN-SP

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Made available in DSpace on 2014-10-09T12:49:28Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:01:16Z (GMT). No. of bitstreams: 0 / Quando um país se torna auto-suficiente em uma parte do ciclo nuclear, quanto à produção de combustível que será usado em suas centrais nucleares para a geração de energia, precisa voltar sua atenção para a melhor forma de armazenar este combustível após a sua utilização. A armazenagem do combustível nuclear queimado é uma prática necessária e utilizada nos dias atuais em todo o mundo como temporária, tanto por países que não têm definido o plano de destinação final, isto é, o repositório definitivo, como também por aqueles que já o possuem. Existem dois aspectos principais que envolvem os combustíveis queimados: um referente à armazenagem do combustível nuclear queimado destinado ao reprocessamento e o outro ao que será enviado para deposição final quando o sítio de deposição definitiva estiver definido, corretamente localizado, adequadamente caracterizado quanto aos diversos aspectos técnicos, e licenciado. Este último aspecto pode envolver décadas de estudos por causa das definições técnicas e normativas em um dado país. No Brasil, o interesse está voltado para a armazenagem dos combustíveis queimados que não serão reprocessados. Este trabalho analisa os tipos possíveis de armazenagem, o panorama internacional e a possível proposta para a futura construção de um sítio de armazenagem temporária no país. / Dissertacao (Mestrado) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares, IPEN/CNEN-SP

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The formation and subsequent burnout behaviour of coal slurry fuel chars has been studied using a suspended single droplet technique and solid sampling techniques in large turbulent diffusion flames. Both these techniques yielded comparable results on the structure of carbonaceous residues from a range of coal slurry fuels containing coals of different rank, size and concentration. The structure and burnout behaviour of all the fuels tested was dependant on coal rank, particle size, and concentration, although these variables did not always produce the same differences in behaviour in coal-oil and coal-water chars. Mid-rank coals, produced swollen well-fused chars which were substantially hollow and incorporated large surface blowholes. Such residues showed little tendency to fragment during combustion. Low and high rank coals produced less swollen chars which were comprised of loosely agglomerated coal particles causing more extensive internal structure and smaller surface blowholes. The furnace results of this and other studies indicate that the latter type of char structure is more conducive to rapid to rapid burnout. Small concentrations of emulsified water in coal-oil slurries were observed to increase the intensity of ebullition during devolatilisation although no evidence was obtained from any of the experimental techniques to suggest that this caused droplet shattering. However, water addition did increase the rate of combustion of coal-oil fuels. A theoretical model of the behaviour of coal slurry fuel chars during combustion has been presented which explains the experimental results in terms of the internal surface area of the char and the availability of this area to the gaseous reactants. It has been concluded that the rate of combustion of coal slurry chars of the size encountered in flames is largely controlled by the rate of internal diffusion of gaseous reactants and reaction within the porous char structure. The different reactivities of coal slurry fuels of different coal ranks has therefore been explained in terms of the various char structures which were observed The beneficial effects of water on the combustion of coal-oil fuels has also been explained within this theory since the addition of water could increase the porosity of the chars. However this has not been confirmed experimentally.

Ph.D. / Fossil fuel burning within residential, industrial and power generation sectors represents a persistent source of air pollution within many parts of South Africa, with the contribution of road transport emissions becoming increasingly important. Additionally, biomass burning, including agricultural burning and wild fires, represents an intermittent but seasonally significant source of atmospheric emissions. Effective air pollution control was historically hindered by the absence of enabling legislation and cooperative governance. The promulgation of the National Environmental Management: Air Quality Act, Act 39 of 2004 represented a major step forward in the evolution of air quality management within South Africa. The historical debate regarding the practicability of effective air quality management is however ongoing. South Africa‟s continued dependence on coal to support its energy-intensive industrial and mining sectors, continued household fuel burning for space heating and cooking purposes within a number of areas, and the dire need for employment creation and focus on rapid development continue to challenge the realisation of air quality improvements. This study investigates the multiple factors contributing to the degradation of air quality in South Africa, and the consequent human health, environmental and economic effects of this pollution. The study critically examines legal, technical and social measures implementable within a tailored system of air quality management which is compatible with socio-economic growth. This thesis integrates and expands on pertinent components of several individual research projects completed by the author during her tenure as a doctoral candidate. The research projects were completed during the period (2002 – 2009) on behalf of various parties including national and local government, standards setting bodies and private organisations. Quantification of health risks associated with significant anthropogenic sources within several South African conurbations, covering 40% of the national population, and the establishment of cost-optimised air pollution interventions, forms a key component of the thesis. In this externalities study, emissions were estimated and effects and associated costs quantified for household fuel burning, power generation, industrial and commercial fuel burning and road transport. Total direct health costs related to inhalation exposures to fuel burning emissions were estimated to be of the order of 3.5 billion 2002 Rands per annum across health effects, conurbations and source groupings assessed. Household fuel burning was estimated to be responsible for about 68% of the total health costs estimated across all conurbations, vehicle emissions for 13%, industrial and commercial fuel burning for 13%, and power generation for about 6%. Emission reduction opportunities were identified and assessed for residential fuel burning, coalfired power generation, road transport, coal-fired industrial boilers and specific individual industries. It was concluded that significant health effect reductions could cost-effectively be achieved through addressing residential fuel burning as a priority. Lower benefit-cost ratios associated with industrial and vehicular interventions are due, in part, to these fuel burning sources having been more effectively regulated historically. The need for effective management of industrial and vehicle emissions is however supported. Based on international experience and local trends in vehicle activity, the contribution of transport emissions will become increasingly ix significant if not adequately addressed. Industrial process emissions unrelated to fuel burning may include significant emissions of criteria pollutants, in addition to trace releases of a wide range of hazardous air pollutants. Internationally, actions taken to address air pollution problems have met with mixed results. Failure to integrate economic considerations into air quality management planning, and to integrate air quality considerations into development planning represent key weaknesses in the strategies implemented. A contribution is made in this thesis by highlighting such lessons and proposing legal, technical and social measures which, when implemented within a rational system of air quality management, are suited to addressing complex air pollution sources without negatively affecting socio-economic prosperity and equity. Components of an effective, affordable and equitable emissions control policy proposed for adoption within South Africa include phased national standards setting, compliance promotion and self-monitoring, market-based instruments, and the implementation of risk-based enforcement and compliance monitoring strategies.

Bibliography: pages 150-156. / The catalytic oligomerization of propene to liquid fuels using synthetic mica montmorillonite (SMM) as well as the effect of incorporating nickel into the lattice and nickel, cobalt and zinc into the interlayer spaces was investigated. NiSMM is more active for propene oligomerization than SMM, although the product selectivity (60% of the oligomers boiled at above 453 K) is similar. The increase in activity of NiSMM is attributed to an increase in the surface acidity of the catalyst. The maximum activity over the nickel exchanged catalyst occurs at a nickel loading of 0.057 wt %. It is proposed that the bond strength of the acidic hydroxyl groups are perturbed by the polarizing effect of the divalent cation (Co, Zn or Ni) present in the interlayer spaces of SMM. The reduction of nickel, ion exchanged into SMM, removes the induction period associated with SMM and increases the catalyst lifetime. However, reduction of the lattice nickel results in a decrease in catalyst lifetime although the Bronsted acidity has increased. It is proposed that the metallic nickel present in reduced NiSMM may promote dehydrogenation of high molecular weight hydrocarbons thus causing rapid deactivation of the catalyst by increasing the formation of "graphitic" coke. The lifetime of NiSMM is greatly reduced by using a wet propene feed and reacting at higher temperatures (443 K) due to the generation of Bronsted sites and increased coke formation rates, respectively. Deactivation of the catalyst is associated with a "graphitic" coke build up. The RON of the petrol fraction is 94.5 and the hydrogenated diesel fraction has a cetane number less than 35.

Energy issues in the United States are currently receiving a very high priority. There is a strong desire to replace fossil fuels with alternative sources of energy since fuel prices are rising dramatically, and for the harming effect on the environment. Biomass is one of the most promising alternative sources of energy. In this study, hydrothermal liquefaction with alcohol co-solvents was applied on giant miscanthus (Miscanthus giganteus) feedstock. All liquefaction experiments were conducted in 5500 series Parr® reactor. The most important parameters that affect the liquefaction process were studied. The yield of the liquefaction process was determined gravimetrically and the produced bio-oils were characterized. Bio-oil obtained at the optimum conditions was upgraded using different solid acid catalysts and the chemical composition for the upgraded bio-oil was determined. In a new study, the solid acids were added directly during the liquefaction process to produce upgraded bio-oil in one liquefaction/upgrading step.

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