Air pollution by sulfur dioxide is of great concern due to its harmful effects on environment, human beings, fauna and flora. Fossil-fuel-fired power plants are one of the major sources of SO2 emissions. Typically the concentration of SO2 in the flue gases of these plants is in the range of 2000 to 20000 ppm. Flue gas desulfurisation is one of the widely practiced strategies to control SO2 emissions. Aqueous phase oxidation of sulfur dioxide catalysed by carbonaceous particles is an attractive alternative to the conventional processes for flue gas desulfurisation because, amongst other reasons, sulfuric acid, the product of aqueous phase oxidation, finds extensive application in industry. In the literature it has been reported that sulfuric acid affects the solubility of sulfur dioxide and that activated carbon catalyses aqueous phase oxidation. However there is hardly any report on the systematic evaluation of the mechanism of the heterogeneous aqueous phase oxidation of sulfur dioxide which takes into account among other factors, the effect of sulfuric acid on the solubility of SO2 (particularly, at low levels of SO2 and sulfuric acid concentrations). Therefore the objective of the present work is to evaluate systematically the aqueous phase oxidation of SO2 in ppm levels with activated carbon as catalyst in a three-phase agitated slurry reactor and to model rigorously the solubility of SO2 in ppm levels in dilute sulfuric acid solutions and to estimate the concerned parameters experimentally. Strong effect of dilute concentrations of sulfuric acid on the solubility of SO2 is analyzed in terms of the influence of the acid on the equilibrium concentrations of the ionic species (HSO3¯ and SO4¯2 formed from the hydrolysis of SO2 (aq) and the dissociation of H2SO4 respectively) in SO2 - dil. H2SO4 systems. The analysis leads to a general expression relating the partial pressure of SO2 in the gas phase to the concentration of total dissolved SO2 and the concentration of sulfuric acid in the solution. Simple equations are obtained from the general expression for the cases of zero and high concentrations of sulfuric acid in the system, which in turn lead to direct experimental determination of the parameters, Henry's law constant and the equilibrium constant of hydrolysis of SO2 (aq). The developed model predicts the present experimental data as well as the data reported in the literature very closely. The dissolution of SO2, the hydrolysis of SO2 (aq) and the dissociation of H2SO4 are found to be instantaneous. From the dependency of the parameters on temperature, the heat of dissolution of SO2 is determined to be -31.47 kJ mol"1 and the heat of hydrolysis to be 15.69 kJ mol"1. The overall heat of solubility of sulfur dioxide is therefore -15.78 kJ mol"1. Preliminary reaction experiments have clearly indicated that SO2 (aq) does not react and HSO3¯ is the only reactant for aqueous phase oxidation of sulfur dioxide catalysed by activated carbon. The non-reactant SO2 (aq) deactivates the oxidation reaction by competing with HSO3¯ for adsorption on the active sites of the catalyst particles. However the catalyst particles become saturated with SO2 (aq) beyond a certain value of its concentration (saturation limit), which depends on temperature. A mechanism is proposed based on these observations to develop a rate model. The rate model also takes into account the effect of the concentration of the product sulfuric acid on the solubility of sulfur dioxide. The model predicts first order in HSO3¯ , half order in dissolved oxygen and a linear deactivation effect of 5O2(ag). The oxidation reaction is evaluated experimentally at various levels of the operating variables such as temperature and the concentrations of sulfur dioxide and oxygen in the inlet gas. In all experiments a pseudo steady-state region is observed where the gas phase concentration of SO2 reaches a steady value but the concentrations of HSO3¯ and total S (VI) in the liquid phase continue to change. Pseudo steady-state considerations lead to the determination of the initial estimates of the parameters of the rate model namely, the rate constant and the deactivation constant. These parameters are estimated from the transient profiles of the product (sulfuric acid) by solving the model equations by Runge-Kutta method along with Marquardt's non-linear parameter estimation algorithm. The predictions of the model with the estimated parameters match very well with the experimentally observed concentration profiles of S(VI) and HSO3 in the liquid phase and SO2 in the gas phase. The deactivation constant in the saturation range is independent of temperature and is 0.27, which indicates that the intrinsic rate constant is about four times greater than the observed rate constant. From Arrhenius equation-type dependency of the parameters on temperature, the activation energy for the oxidation reaction is determined to be 93.55 kJ mol"1 and for deactivation to be 21.4 kJ mol"1. The low value of activation energy for deactivation suggests a weak dependency of the deactivation on temperature, which perhaps is due to the weak nature of the chemisorption of SO2 (aq) on carbon.

Human mesenchymal stem cells (hMSCs) are a promising candidate for cell-based therapies given their therapeutic potential and propensity to grow in vitro. However, to generate the cell numbers required for such applications, robust, reproducible and scalable manufacturing methods need to be developed. To address this challenge, the expansion of hMSCs in a microcarrier-based bioreactor system was investigated. Initial studies performed in T-flask monolayer cultures investigated the effect of key bioprocess parameters such as dissolved oxygen concentration (dO2), the level of medium exchange and the use of serum-free media. 20 % dO2 adversely impacted cell proliferation in comparison to 100 % dO2, whilst FBS-supplemented DMEM was found to be the most consistent and cost-effective cell culture medium despite the advances in serum-free cell culture media. Several microcarriers were screened in 100 mL agitated spinner flasks where Plastic P102-L was selected as the optimal microcarrier for hMSC expansion given the high cell yields obtained, its xeno-free composition and effective harvest capacity. The findings from the initial small-scale studies culminated in the successful expansion of hMSCs on Plastic P102-L microcarriers in a fully equipped 5 L stirred-tank bioreactor (2.5 L working volume), the largest reported volume for hMSC microcarrier culture to date. A maximum cell density of 1.68 x 105 cells/mL was obtained after 9 days in culture; further growth was limited by the low glucose concentration and lack of available surface area. A novel, scalable harvesting method was also developed, allowing for the successful recovery of hMSCs. Importantly, harvested hMSCs retained their immunophenotype, multipotency and ability to proliferate on tissue culture plastic.

This thesis examines the bioleaching of six different Canadian nickel sulphide ores at pH levels above what is generally considered optimum (~ 2). The majority of work discussed in this thesis was conducted with a low-grade metamorphosed ultramafic nickel sulphide ore from Manitoba, Canada (Ore 3), which is not currently exploitable with conventional technologies. The ore contains 21% magnesium and 0.3% nickel. Nickel is the only significant metal value, and is present primarily as pentlandite. A substantial fraction of the magnesium is present as the serpentine mineral lizardite, making processing difficult with conventional pyro- and biohydrometallurgical techniques. The work with this ore has two equally important objectives: to minimize magnesium mobilization and to obtain an acceptable level of nickel extraction. Batch stirred-tank bioleaching experiments were conducted with finely ground ore ( 147 µm) with temperature and pH control. The first phase of experimentation examined the effect of pH (2 to 6) at 30 °C, and the second phase examined all combinations of three pH levels (3, 4 and 5) and five temperatures (5, 15, 22.5, 30, and 45 °C).

A theoretical study on the hydrodynamics of mixing processes in stirred tanks is described. The primary objective of this study is to investigate flow field and power consumption generated by the six blades Rushton turbine impeller in baffled, flat-bottom cylindrical tank both at laminar and turbulent flow regime both qualitatively and quantitatively. Experimental techniques are expensive and time consuming in characterizing mixing processes. For these reasons, computational fluid dynamics (CFD) has been considered as an alternative method. In this study, the velocity field and power requirement are obtained using FASTEST, which is a CFD package. It employs a fully conservative second order finite volume method for the solution of Navier-Stokes equations. The inherently time-dependent geometry of stirred vessel is simulated by a multiple frame of reference approach. The flow field obtained numerically agrees well with those published experimental measurements. It is shown that Rushton turbine impeller creates predominantly radial jet flow pattern and produces two main recirculation flows one above and the other below the impeller plane. Throughout the tank impeller plane dimensionless radial velocity is not affected significantly by the increasing impeller speed and almost decreases linearly with increase in radial distance. Effect of the baffling on the radial and tangential velocities is also investigated. It is seen that tangential velocity is larger than radial velocity at the same radial position in unbaffled system. An overall impeller performance characteristic like power number is also found to be in agreement with the published experimental data. Also power number is mainly affected by the baffle length and increase with increase in baffle length. It is concluded that multiple frame of reference approach is suitable for the prediction of flow pattern and power number in stirred tank.

Pour faire face à l’épuisement des combustibles fossiles conventionnels et aux préoccupationsenvironnementales dont le réchauffement climatique, de nouveaux carburants issus de la biomasse sontutilisés purs ou comme co-carburants ; d’autres sont envisagés pour le futur. Une meilleure connaissance dela cinétique chimique d’oxydation des composés présents dans ces carburants alternatifs est indispensable.L’objectif de cette thèse est donc d’obtenir de nouvelles bases de données expérimentales et d’élaborer desmécanismes cinétiques d’oxydation des constituants de ces nouveaux carburants. Des molécules de deuxfamilles chimiques, à savoir les esters méthyliques et les alcools, ont été sélectionnées. L’oxydation de cescomposés purs ou en mélanges a été étudiée en réacteur auto-agité à haute pression (10 atm) et dans un largedomaine de températures (530-1250 K) et de richesses (ca. 0,3-4). Les profils de concentration des réactifs,produits et principaux intermédiaires stables ont été obtenus par spectroscopie d’absorption infrarouge àtransformée de Fourier (IRTF) et chromatographie en phase gazeuse (GC-FID-TCD-MS). Les résultatsobtenus ont permis de proposer des modèles cinétiques permettant de simuler avec un bon accord une grandepartie des résultats expérimentaux obtenus au cours de cette thèse. Les analyses cinétiques ont permis dedéterminer les principales voies de consommation de ces composés (principalement des mécanismes deperoxydation-isomérisation à basse température et de métathèse puis décomposition par β-scission à hautetempérature). Elles ont permis d’identifier les réactions les plus influentes (réactions de métathèse etréactions impliquant particulièrement les composés de la base C0-C2). / To overcome the problems of conventional fossil fuels depletion and environmental issues includingglobal warming, new fuels derived from biomass are used pure or in blends; others are proposed for thefuture. A good knowledge of the chemical kinetics of oxidation of components present in these alternativefuels is necessary. The aim of this work is to obtain a new experimental database and to build a chemicalkinetic reaction mechanism for the combustion of these new fuels. Molecules of two functional groups werechosen: methyl esters and alcohols. The kinetics of oxidation of these compounds were studied in a Jet-Stirred Reactor at high-pressure (10 atm), over the temperature range 530-1250 K, for several equivalencesratios (ca. 0.3-4) Concentration profiles of reactants, products and main stable intermediates were obtainedby probe sampling and FTIR (Fourier transform infrared spectroscopy) and GC-FID-TCD-MS analyses. Theresults allowed proposing detailed kinetics models that successfully simulate concentration profilesdetermined by Jet-Stirred Reactor method. The kinetic analyses allowed delineating the main oxidation pathsof consumption (peroxidation-isomerisation at low temperature and beyond, metathesis followed by betascissiondecomposition), and identifying the most influencing reactions for the oxidation rate of the fuels, i.e.metathesis reactions with C0-C2 species.

Thesis (DTech (Electrical Engineering))--Cape Peninsula University of Technology, 2016. / Majority of the industrial systems encountered are significantly non-linear in nature, so if they are synthesised and designed by linear methods, then some of salient features characterising of their performance may not be captured. Therefore designing a control system that captures the nonlinearities is important. This research focuses on the control design strategies for the Continuous Stirred Tank Reactor (CSTR) process. To control such a process a careful design strategy is required because of the nonlinearities, loop interaction and the potentially unstable dynamics characterizing the system. In these systems, linear control methods alone may not perform satisfactorily. Three different control design strategies (Dynamic decoupling, Decentralized and Input-output feedback linearization controller) are proposed and implemented .in the Matlab/Simulink platform and the developed strategies are then deployed to the design of distributed automation control system configuration using the IEC 61499 standard based functional block programming language. Twin CAT 3.1 system real-time and Matlab/Simulink (www.mathworks.com) environment are used to test the effectiveness of the models The simulation results from the investigation done between Simulink and TwinCAT 3 software (Beckhoff Automation) platforms in the case of the model transformation and closed loop simulation of the process for the considered cases have shown the suitability and the potentials of merging the Matlab/Simulink control function blocks into the TwinCAT 3.1 function blocks in real-time. The merits derived from such integration imply that the existing software and software components can be re-used. This is in line with one of the IEC 6144 standard requirements such as portability and interoperability. Similarly, the simplification of programming applications is greatly achieved. The investigation has also shown that the integration the of Matlab/Simulink models running in the TwinCAT 3.1 PLC do not need any modification, hence confirming that the TwinCAT 3.1 development platform can be used for the design and implementation of controllers from different platforms. Also, based on the steps required for model transformation the between the Matlab/Simulink to the TwinCAT 3 functional blocks, the algorithms of the control design methodologies developed, simulation results are used to verify the suitability of the controls to find whether the effective set-point tracking control and disturbance effect minimisation for the output variables can be achieved in real-time using the transformed Simulink blocks to the TwinCAT 3 functional blocks, then downloaded to the Beckhoff CX5020 PLC for real-time execution. Good set-point tracking control is achieved for the MIMO closed loop nonlinear CSTR process for the considered cases of the developed control methodologies. Similarly, the effects of disturbances are investigated. TwinCAT functional modules achieved good set-point tracking with these disturbances minimization under all the cases considered.

Este trabalho estudou a aplicação de oito métodos clássicos de escalonamento de tanques condicionadores, testando sua validade para dois tanques de geometria semelhante, mas com diferentes volumes (V1=10 e V2=49 decímetros cúbicos). No interior dos tanques, operavam impulsores (diâmetro D1=0,078m x D2=0,132m) que exibiam três distintos desenhos (2 pás versus 4 pás inclinadas em 45 graus versus turbina de Rushton). Sua rotação (N1 no tanque menor x N2 no tanque maior) visava à suspensão de partículas grossas de apatita (diâmetro médio = 254 micrometros) em polpas com 40% de sólidos em massa. Para balizar o escalonamento, adotou-se como variável de controle a mínima rotação do impulsor (Njs) que é capaz de fazer com que nenhuma partícula repouse no fundo do tanque por mais do que 1 ou 2 segundos (Critério 1-s), além de perfis axiais de distribuição de sólidos e a extensão da Zona Turbulenta versus Zona Quiescente no interior dos tanques. A diferença entre o valor previsto de Njs para o tanque de 49 decímetros cúbicos (N2) pelos métodos de escalonamento versus o valor de Njs (N2) determinado experimentalmente foi expressa como erro percentual (E). Consideraram-se como adequados para a aplicação que constitui o objetivo desta dissertação todos os métodos que exibiram E menor que 10%. Para o impelidor de 2 pás inclinadas, a adequação do método baseado na constância da razão potência/volume (E=2%) e também do método empírico de Rautzen (E=6%), indica a expressão N2=N1.(D1/D2) com seu expoente da relação entre os diâmetros variando entre 0,67 e 0,75 para a aplicação desejada. Considerando o impulsor de 4 pás inclinadas, a adequação do método da constância da razão potência/volume (E=4%); assim como dos métodos empíricos de Rautzen (E=0%) e Zwietering (5%), sugere o uso da expressão N2=N1.(D1/D2) com seu expoente da relação entre os diâmetros variando entre 0,67 e 0,85. Para a turbina de Rushton, o único método que exibiu E menor que 10% foi o da constância da relação potência/volume (E=8%), cuja expressão é N2=N1.(D1/D2) com seu expoente da relação entre os diâmetros igual a 0,67. Uma vez que a determinação do valor real de N2 foi baseada numa técnica experimental influenciada pelas limitações do observador, pode-se inferir que uma expressão geral de escalonamento do tipo N2=N1.(D1/D2) com seu expoente da relação entre os diâmetros igual a 0,75 atende aos propósitos desta aplicação. Por outro lado, o uso da relação P/V provê um critério mais objetivo para se balizar o escalonamento, haja vista que ele se adequou a todos os três tipos de impelidores contemplados por este estudo. / This work has studied the application of eight classical methods appointed by literature to accomplish the scale-up of stirred tanks which aimed to suspend slurries of 40% of solids, containing coarse (mean diameter=254 micrometers) apatite particles. The validity of the methods was accomplished by using two tanks of similar geometry but different capacity (V1=10 e V2=49 cubic decimeter), together with impellers of different diameter (D1=0,078m versus D2=0,132m) and design (turbine of 2 or 4 blades inclined at 45 degrees and Rushton turbine). To assist the process of validation, the impeller speed (Njs) under which no particle rests on the bottom of the tank for more than 1-2 seconds (1-s Criterium) was used together with the axial profile of solids percent distribution plus the extension of the turbulent versus quiescent zones within the two tanks. For any of the eight scale-up methods, the difference between the predicted value of Njs (N2) for the 49 cubic decimeter tank and the actual value (experimental) of the same variable was determined and its magnitude was expressed in terms of the percent error (E). The methods that yielded E less than 10% were considered as suitable for the aimed application. Considering the 2-inclined blade impeller, low value of E yielded by the method based on the constancy of the ratio power/volume (E=2%) and also by the empiric method of Rautzen (E=6%) indicate that the expression N2=N1.(D1/D2) with its exponent of the relation between diameters ranging between 0,67 and 0,75 is suitable for the desired application. Regarding the 4-inclined blade impeller, because the method based on the constancy of the ratio power/volume (E=4%) and also the empiric methods of Rautzen (E=0%) and Zwietering (E=5%) yielded the lowest values of E, the expression N2=N1.(D1/D2) with its exponent of the relation between diameters ranging between 0,67 and 0,85 is suitable for the aimed application. Moreover, for the Rusthon turbine, only the method based on the constancy of the ratio power/volume (E=8%) was adequate for the aimed application and, thus, the expression N2=N1.(D1/D2) with its exponent of the relation between the diameters equal to 0,67 is suitable for the purpose of this dissertation. Once the actual value of N2 is determined by visual observation, it is not possible to get very accurate results. This way, a generic scale-up expression is proposed: N2=N1.(D1/D2) with its exponent of the relation between the diameters equal to 0,75. On the other hand, the ratio P/V may provide a more objective criterium for scale-up, because the three sort of impellers used in this study yielded E less than 10% when the power/volume method was applied for the purpose of scale-up.

In an effort to reduce NOX emissions both in the landing and take-off (LTO) cycle as well as in cruise, significant research has been conducted on novel aero-engine low emissions combustor design concepts. Preliminary combustor design and emissions prediction software tools are becoming increasingly important during the conceptual design phase of aero-engine combustors. They allow a large number of designs to be explored, in a relatively short amount of time, thereby identifying the most promising designs to consider for further development. There are three methods for NOX emission prediction; correlations, stirred reactor models and CFD models. Correlation methods are derived from experimental results and are therefore only applicable for combustors for which data is available. The stirred reactor modelling approach provides a reasonably good compromise with respect to computational time and robustness relative to correlation and CFD based methods. The stirred reactor method assumes finite rate chemistry inside the combustor using simplified chemical kinetic models. The basic concept of the reactor-based method is to split the combustor into a number of reactors (perfectly or partially stirred) to compute the overall emissions. The primary objective of this doctoral research was to assess the suitability and limitations of the stirred reactor modelling approach to predict NOX emissions of a Rich-Burn Quick-Quench and Lean-Burn (RQL) combustor concept. The geometry of the RQL combustor and the model constraints were assumed from a NASA test rig experiment. The stirred reactor emission prediction model developed was verified using this test data. The results suggest that, based on the modelling assumptions made, the stirred reactor modelling approach is able to capture the trends of emissions (with changing boundary conditions) even though there are discrepancies in the absolute values. This suggests that the stirred reactor model is a useful tool during the preliminary design phase to quantify the impact of changes in boundary conditions/design parameters on changes in NOX emissions.

Research into hydrate production technologies has increased in the past years. While many technologies have been presented, there is no consensus on which reactor design is best for each potential application. A direct experimental comparison of hydrate production technologies has been carried out in between a variety of reactor configurations at similar driving force conditions. Three main reactor types were used: a stirred tank, a fixed bed and a bubble column and compared different phase contacting patterns for the stirred tank and bubble column. In the initial phase of hydrate formation in a stirred tank, formation was mass and heat transfer limited at the lower stirring speed, and heat transfer limited at the higher stirring speed. After more than 10% of the water had been converted to hydrate, formation was mass transfer limited regardless of the other conditions. Neither the use of a gas inducing impeller, nor a 10 wt% particle slurry significantly affected hydrate formation rates; however, the particle slurry did lower the induction time. Due to the poor scale-up of impeller power consumption in a stirred tank, a semi-batch fixed bed was studied since it does not require any power input for mixing. The significantly slower rates of formation observed in the semi-batch fixed bed, as well as the lost reactor capacity to particles, mean that this type of system would require a much larger reactor. Faster volume and power normalized rates of hydrate formation were observed in the bubble column than in a stirred tank at similar mass transfer driving force conditions. Higher conversions of water to hydrate were observed in the bubble column because mixing was accomplished by bubbling gas from the bottom rather than by an impeller. The highest conversions of water and gas were achieved during a later stage of accelerated hydrate formation, indicating an optimal hydrate fraction for continuously operated bubble column reactors. The second stage of hydrate formation occurred more frequently at higher gas flowratess. Therefore, the increased water conversion and single-pass gas conversion justify the increased energy input required by the higher gas flowrate. Balancing the rates of mass transfer and heat removal was also critical for optimal bubble column as insufficient mass transfer would result in a lower rate of formation and insufficient heat transfer would cause previously formed hydrates to dissociate. The addition of 10wt% glass beads to the reactor promoted hydrate formation; however, it did not do so sufficiently to make up for the loss in reactor capacity or the increased energy requirement.

Enzymes, as nature’s catalysts, show remarkable abilities that can revolutionize the chemical, biotechnological, bioremediation, agricultural and pharmaceutical industries. However, the narrow range of stability of the majority of described biocatalysts limits their use for many applications. To overcome these restrictions, extremozymes derived from microorganisms thriving under harsh conditions can be used. Extremophiles living in high salinity are especially interesting as they operate at low water activity, which is similar to conditions used in standard chemical applications. Because only about 0.1 % of all microorganisms can be cultured, the traditional way of culture-based enzyme function determination needs to be overcome. The rise of high-throughput next-generation-sequencing technologies allows for deep insight into nature’s variety. Single amplified genomes (SAGs) specifically allow for whole genome assemblies from small sample volumes with low cell yields, as are typical for extreme environments. Although these technologies have been available for years, the expected boost in biotechnology has held off. One of the main reasons is the lack of reliable functional annotation of the genomic data, which is caused by the low amount (0.15 %) of experimentally described genes. Here, we present a novel annotation algorithm, designed to annotate the enzymatic function of genomes from microorganisms with low homologies to described microorganisms. The algorithm was established on SAGs from the extreme environment of selected hypersaline Red Sea brine pools with 4.3 M salinity and temperatures up to 68°C. Additionally, a novel consensus pattern for the identification of γ-carbonic anhydrases was created and applied in the algorithm. To verify the annotation, selected genes were expressed in the hypersaline expression system Halobacterium salinarum. This expression system was established and optimized in a continuously stirred tank reactor, leading to substantially increased cell amounts and protein yields. The resulting gene expression products were assessed for function in vivo and/or in vitro. Our functional evaluation of the tested genes confirmed our annotation algorithm. Our developed strategy offers a general guide for using SAGs as a source of scientific and industrial investigations into “microbial dark matter” and may help to develop new catalysts, applicable for novel reactions in green chemistry.