CoordenaÃÃo de AperfeiÃoamento de Pessoal de NÃvel Superior / A reaÃÃo de sÃntese de Fischer-Tropsch tem merecido grande atenÃÃo pela sua aplicaÃÃo no Ãmbito tecnolÃgico e cientÃfico. Este interesse està associado à conversÃo do gÃs natural em produtos lÃquidos de alta qualidade (gasolina e diesel) e elevado valor agregado. No presente trabalho à descrito a metodologia empregada na sÃntese e caracterizaÃÃo de catalisadores bimetÃlicos, com alto teor da fase ativa de ferro e cobalto, usados na sÃntese de Fischer-Tropsch, suportados em sÃlica promovidos com potÃssio e cobre com diferentes proporÃÃes em base molar. O uso de catalisadores de ferro utilizados na sÃntese de Fischer-Tropsch tem sido estudado por muitos pesquisadores, os resultados tÃm mostrado que estes possuem um desempenho satisfatÃrio na produÃÃo de combustÃveis lÃquidos. Entretanto, pesquisas mostram que os catalisadores de cobalto sÃo mais eficientes na produÃÃo de hidrocarbonetos de cadeia longa e linear em relaÃÃo ao ferro. Contudo, catalisadores a base de cobalto sÃo mais caros comparados aos de ferro. Uma relaÃÃo custo/benefÃcio tem que ser atingida na fabricaÃÃo de catalisadores de tal forma que tenhamos uma otimizaÃÃo da produÃÃo de combustÃveis sintÃticos de elevado peso molecular sem muitos gastos com o catalisador. Pretende-se com esta discussÃo, identificar possÃveis vias para o desenvolvimento de catalisadores mais ativos e seletivos, variando a composiÃÃo do promotor estrutural para fins de otimizar a distribuiÃÃo dos produtos (diesel e graxa). A reaÃÃo foi conduzida em um reator de leito de lama. O estudo seguiu um planejamento experimental do tipo fatorial quadrado com ponto central e os resultados foram analisados baseados na metodologia de anÃlises de superfÃcies de respostas. Os efeitos das diferentes condiÃÃes operacionais (temperatura e pressÃo) e dos diferentes teores de potÃssio e cobre na distribuiÃÃo dos produtos lÃquidos foram comparados baseados nos cromatogramas, nÃmero mÃdio de carbono (Nn). Diante dos testes realizados com os catalisadores bimetÃlicos (Fe/Co) dopados com diferentes teores de potÃssio e/ou cobre, chegou-se a uma melhor relaÃÃo entre os metais (K,Cu) para sÃntese de um catalisador mais eficiente (50Fe/50Co/12K/5Cu/139SiO2). Sendo que o objetivo desta formulaÃÃo bimetÃlica, obter vantagens de possÃveis efeitos sinergÃticos entre os dois metais (Fe/Co) e seus promotores estruturais. / The reaction of Fischer-Tropsch synthesis has received great attention for its application in technology and science. This interest is associated with conversion of natural gas into high quality liquid products (gasoline and diesel) and high added value. In the present paper describes the methodology employed in the synthesis and characterization of bimetallic catalysts with high levels of the active phase of iron and cobalt, used in the synthesis of Fischer-Tropsch, supported on silica promoted with potassium and copper with different ratios on a molar basis. The use of iron catalysts used in the Fischer-Tropsch synthesis has been studied by many researchers, the results have shown that these have a satisfactory performance in the production of liquid fuels. However, studies have shown that cobalt catalysts are most effective in producing long-chain hydrocarbons and linear with respect to iron. However, the cobalt-based catalysts are more expensive compared to iron. A cost / benefit ratio has to be reached in the manufacture of catalysts which have such an optimization of production of synthetic fuels of high molecular weight inexpensively with the catalyst. The intention with this discussion, identify possible pathways for the development of more active and selective catalysts, varying the composition of the promoter structure for purposes of optimizing the distribution of products (diesel and grease). The reaction was conducted in a reactor bed of mud. The study followed an experimental planning factorial central square and the results were analyzed based on the methodology of the analysis of response surfaces. The effects of different operating conditions (temperature and pressure) and different concentrations of potassium and copper in the distribution of liquid based on the chromatograms were compared, average carbon number (Nn). Before the tests with the bimetallic catalysts (Fe / Co) doped with different concentrations of potassium and / or copper, it was a better relationship between the metals (K, Cu) for the synthesis of a more efficient catalyst (50Fe/50Co/12K/5Cu/139SiO2). Since the goal of this formulation bimetallic take advantage of possible synergistic effects between the two metals (Fe / Co) and its structural promoters.

Thesis (MScEng)--Stellenbosch University, 2014. / ENGLISH ABSTRACT: Traditionally nuclear reactor power plants have been optimised for electrical power generation only. In the light of the ever-rising cost of dwindling fossil fuel resources as well the global polluting effects and consequences of their usage, the use of nuclear energy for process heating is becoming increasingly attractive. In this study the use of a so-called cogeneration plant in which a nuclear reactor energy source is optimised for the simultaneous production of superheated steam for electrical power generation and process heat is considered and analysed. The process heat superheated steam is generated in a once-through steam generator of heat pipe heat exchanger with intermediate fluid while steam for power generation is generated separately in a once-through helical coil steam generator. A 750 °C, 7 MPa helium cooled HTMR has been conceptually designed to simultaneously provide steam at 540 °C, 13.5 MPa for the power unit and steam at 430 °C, 4 MPa for a coal-to-liquid fuel process. The simulation and dynamic control of such a typical cogeneration plant is considered. In particular, a theoretical model of a typical plant will be simulated with the aim of predicting the transient and dynamic behaviour of the HTMR in order to provide guideline for the control of the plant under various operating conditions. It was found that the simulation model captured the behaviour of the plant reasonably well and it is recommended that it could be used in the detailed design of plant control strategies. It was also found that using a 1500 MW-thermal HTMR the South African contribution to global pollution can be reduced by 1.58%. / AFRIKAANSE OPSOMMING: Tradisioneel is kernkragaanlegte vir slegs elektriese kragopwekking geoptimeer. In die lig van die immer stygende koste van uitputbare fossielbrandstohulpbronne asook die besoedelingsimpak daarvan wêreldwyd, word die gebruik van kernkrag vir prosesverhitting al hoe meer aanlokliker. In hierdie studie word die gebruik van ‘n sogenaamde mede-opwekkingsaanleg waarin ‘n kernkragreaktor-energiebron vir die gelyktydige produksie van oorverhitte stoom vir elektriese kragopwekking en proseshitte oorweeg ontleed word. Die oorvehitte stoom word in ‘n enkeldeurvloei-stoomopwekking van die hittepyp-hitteruiler met tussenvloeistof opgewek en stoom vir kragopwekking word apart in ‘n enkeldeurvloei-spiraalspoel-stoomopwekker opgewek. ‘n 750 °C, 7 MPa heliumverkoelde HTMR is konseptueel ontwerp vir die gelytydige veskaffing van stoom by 540 °C, 13.5 MPa, vir die kragopwekkings eenheid, en stoom by 430 °C, 4 MPa, vir ‘n steenkool-tot-vloeibare (CTL) brandstoff proses. Die simulasie en dinamiese beheer van ‘n tipiese HTMR mede-opwekkingsaanleg word beskou. ‘n die besonder word ‘n teoretiese model van die transiënte en dinamiese gedrag van die aanleg gesimuleer om sodoene riglyne te identifiseer vir die ontwikkeling van dinamiese beheer strategië vir verskillende werkstoestande van die aanleg. Daar was ook gevind dat die simulasie model van die aanleg se gedrag goed nageboots word en dat dit dus gebruik kan word vir beheer strategie doeleindes. Indien so ‘n 1500 MW-termies HTMR gebruik word sal dit die Suid Afrikaanse besoedling met 1.58% sal kan verminder.

Thesis (MBA)--Stellenbosch University, 2014. / Broad-based Black Economic Empowerment (B-BBEE) not only aims to readdress the racial imbalances of the apartheid era, but also seeks to promote social responsibility and empowerment of historically disadvantaged South African (HDSA) communities (Esser & Dekker, 2008). The transformation journey within the South African Liquid Fuels Sector has been a difficult and lengthy one. The South African Liquid Fuels Sector was amongst the first to receive its own Black Economic Empowerment (BEE) sector charter (Liquid Fuels Charter) in 2000. Although numerous transformation milestones have been achieved, the sector has been criticised for its slow pace in advancing transformation, which has in part contributed to the amendment of the B-BBEE Codes in 2013. The argument of slow transformation can be attributed to obstacles faced by those in industry tasked with implementing B-BBEE. There has been a deficiency in studies that have investigated transformation and the implementation of B-BBEE within the sector. As a result, the central objective of this study was to explore the B-BBEE implementation challenges faced by companies within the liquid fuels sector. A qualitative approach was employed for the collection of primary data and involved interviews with eight top and senior management representatives of Chevron South Africa (Pty) Ltd. The results emanating from the study revealed numerous implementation challenges. The study together with literature reviewed, highlights the need to address these challenges in order for B-BBEE implementation to yield the desired results for all stakeholders within the South African Liquid Fuels Sector. The study concludes that a lack of understanding of B-BBEE policy; alignment of internal party interests; overcoming internal biases; skills shortages and lack of experience by Black individuals; involvement of senior management in implementation process; co-ordination and structure required in B-BBEE implementation execution; communication within organisations; diversity/cultural awareness; and B-BBEE policy issues and skills attraction and retention are some of the issues impacting B-BBEE implementation within the South African Liquid Fuels Sector.

Within this body of work several series of experiments will investigate the nature of complex combustion in an experimental single-cylinder engine emulating a modern passenger car size compression-ignition (CI) engine. Regimes of single, piloted single and piloted split-main injections will be tested and compared in terms of combustion characteristics, specific emission output and cyclic behaviour to determine how increased injection complexity affects the emissions and output of the modern CI engine. Through these tests, the effect of fuel-line stationary waves will be demonstrated and investigated, showing conclusively that optimised engine calibration is essential to account for injector-generated waves in any multiple injection scenario. This data will then be confirmed with a dedicated analysis using an injector rate measuring tube. The tests will then be expanded to include examination into the behaviour of injector needle-lift standard deviation over its operating cycle, in-cylinder pressure standard deviation behaviour and trends over the combustion cycle as well as IMEP variability. Through these tests a novel method to detect start of combustion will be proposed and compared to conventional methods. Low temperature combustion (LTC) will be tested under incremental injection complexity. Tests will be optimised for combustion phasing and injection pressure, with a view to analysis of emissions, output and cyclic behaviour to establish whether the knowledge gained about conventional combustion holds true under LTC. Optimization of engine parameters will be shown to result in easier to implement LTC regimes with superior emissions characteristics. Finally, LTC tests will be expanded to include 30% and 50% by volume gas-to-liquid fuel (GTL) blends in order to determine whether fuel characteristics further influence emissions, output and cyclic behaviour in LTC through complex injection regimes. How GTL-blend ratio affects trends in emissions and cyclic behaviour will also be examined and compared to conventional diesel fuel.

The present work is concerned with fundamental studies on the liquid fuel transport in the intake manifold of small carburetted engines. This work is motivated by the need for development of technologies to meet the stringent cold-start emission norms that are to be prescribed for two-wheelers in particular. More specifically, visualization studies conducted in a transparent manifold made of quartz in a small four-stroke 110-cc two-wheeler engine have shown the presence of gasoline films on the walls of the inlet manifold under cold start conditions. Advanced Laser diagnostic techniques such as Planar Laser Induced Fluorescence (PLIF) have been utilized to measure the thickness of the fuel films. The Sauter Mean Diameter for the fuel droplets at the carburettor exit is measured using Laser Shadowgraphy technique. It is observed that the films are present both at idling conditions and under load. This large amount of liquid fuel entering the engine leads to incomplete combustion and higher emissions of unburned hydrocarbons. A detailed analysis of the effects of heating the inlet manifold has been performed. The potential of this manifold heating strategy in reducing hydrocarbon emissions has been assessed and found to be promising. In addition, a need of proper control of the fuel exiting the carburettor is shown to reduce emissions and increase fuel efficiency.

Atomization characteristics of liquid fuel sprays control combustion efficiency and emissions in engines. The present work is motivated by the need to study the atomization and spray structure of vegetable oil biofuels for which no data in the literature exists. In this work, various laser-based diagnostic techniques such as laser shadowgraphy, Particle/Droplet Image Analysis (PDIA) and Laser Sheet Dropsizing (LSD) are applied for studying atomization characteristics, tip penetration, droplet size and liquid volume fraction of Pongamia vegetable oil (SVO) and its blends with diesel. A constant volume high pressure spray visualization chamber is designed and fabricated to study SVO sprays at high gas pressure and temperature conditions. This optical chamber can be used for gas pressures up to 60 bar and temperatures up to 600 K. Optical access inside the chamber is provided through four quartz windows to perform various optical spray diagnostic studies. A high pressure spray injection facility based on components of common rail diesel injection system is designed. This facility can provide an injection pressure of up to 1700 bar with independent control over injection duration and timing. A marked difference is observed between diesel and SVO spray structures under atmospheric gas pressure condition. A very interesting observation related to the behavior of 100% SVO fuel when sprayed into atmospheric pressure is the presence of an intact liquid core even at injection pressure as high as 1600 bar. The presence of liquid core at high injection pressures is attributed to the high viscosity of SVOs and the non-Newtonian behavior of these oils under high pressure and shear. The spray characterization of the oil and its blends at high gas pressure shows that although the atomization is dramatically different from that at atmospheric gas pressure, it is still incomplete even at very high injection pressures. For a gas pressure of 30 bar, it is observed that the Sauter Mean Diameter (SMD) for Pongamia oil is more than twice that of diesel. A new method of simultaneously obtaining two-dimensional droplet size and quantitative liquid volume fraction data in sprays has been developed. Measurements with this method reveal a higher liquid volume fraction at the central axis of spray for Pongamia oil compared to that of diesel indicating potentially poor air-fuel mixing. The experimental data obtained and the spray tip penetration correlations developed for the vegetable oils and blends serve as useful inputs for fuel injection and engine system designers.

Cílem práce bylo vytvořit základní koncept integrovaného výměníku tepla pro solí chlazený reaktor vyvíjený společností Terrestrial Energy s využitím programu Promex. První kapitola se zabývá historií a současnou situací v oblasti výzkumu malých modulárních reaktorů chlazených fluoridovými solemi. Ve druhé kapitole jsou popsány vlastnosti fluoridových solí a konstrukčních materiálů. Poslední kapitola se zabývá simulací tepelného výměníku pomocí programu Promex, validací modelu, transformací protiproudého výměníku na výměník s U trubkami a vizualizací výměníku s použitím CAD Invetoru.

This work thoroughly analyzes a previously created computational model for predicting characteristic properties of the combustion process in an experimental combustion chamber. Any found shortcomings of the original model are removed and the model is further improved prior to its application on 11 real cases of combustion tests performed at various conditions and with various fuels. Data provided by the model are confronted with the data obtained during the combustion tests and the model accuracy is evaluated, based on local heat flux along the length of the combustion chamber. Finally, the overall usefulness of the model is determined by the means of evaluating the acquired accuracy values, and further possibilities of model improvement and use are presented.