Motionless mixers are pipe inserts that generate high rates of energy dissipation compared to an empty pipe, and more uniformly than in a stirred tank. Four types of motionless mixer were chosen for investigation: the Kenies and HEV mixers (manufactured by Chemineer); the SMV and SMXL mixers (from Sulzer). A range of experimental techniques were used to investigate the performance of the mixers andthe results interpreted by using appropriate correlations and insights from turbulence theory. New data is presented on LOA measurements in two motionless mixer flow fields. The mixer flow patterns, turbulent diffusivities and local turbulent energy dissipation rates are now available for the Kernes andHEV mixers. Correlations ofthe type developed for pipe mixers (whereaxial and radial dispersion can be expressed in terms ofthe square root of the friction factor) were found to be inappropriate for characterising the macromixing data of motionless mixers. However, the prediction of axial dispersion coefficients, based onthe analysis ofRTD measurements presented inthiswork, isnowpossible. All the motionless mixers tested have narrow RTDs in the fully turbulent regime. RTDs differ significantly in the transitional regime. It wasfound that the total power consumption of a motionless mixer is not a good indicator of its likely mixing performance for macro-, meso-Iinertial-convective mass transfer) or micrornixing limited applications. As a consequence, designing or retro-fitting a motionless mixer on the basis ofpressure drop information alone is not recommended. The turbulence generating efficiency (T}) of a motionless mixer is defined as; the ratio of the average turbulent energy dissipation rate ina mixer, to thetotal energy dissipation rate (calcluated from pressure drop measurements). Approximate values of n (determined from the results of micromixing-controlled azo-coupling experiments) are: 80% (HEV mixer); 70%(SMXL mixer); 60% (Kenies mixer validated at two scales); 15% (SMV mixer). For fast chemical processes, the optimum feed position into a motionless mixer is several diameters downstream of the first mixer element, and not upstream of the mixer as often recommended. . Thecharacteristic time-scales of the different mixing mechanisms have been derived. Comparison of the time-scales revealed the rate-limiting (i.e. slowest) mixing step in the azo-coupling experiments carried out in all four mixers. The scale-up/-down criteria for motionless mixers in semi-batch or continuous operation have been derived for macromixing, mesomixing and micromixing limited processes. The scaling rules for macromixing and mesomixing are the sam

The demand for new methods through which important enantiopure compounds can be produced is increasing within the chemical industry. In this regard, one group of interesting compounds are enantiopure carboxylic acids as traditional methods towards producing these compounds that rely on a process known as enantioselective decarboxylative protonation (EDP) are often insufficient due to a combination of factors including low yields, low enantioselectivities, the need for environmentally deleterious reaction conditions and high costs. Due to the shortcomings of these synthetic techniques, the application of biological systems is an alternative method that has come to the forefront of current research, which is because biological systems often boast a number of advantages over traditional chemical methods. Described within this thesis is one such biological method towards the production of enantiopure carboxylic acid compounds via EDP, a method that utilises the enzyme aryl malonate decarboxylase (AMDase). This research follows on from previous work detailing the mechanism this enzyme utilises toperform decarboxylation reactions and specifically looks into the substrate specificity that thisenzyme possesses. This work allows us to see how flexible this method is with regards to theproduction of a range of different carboxylic acid products, which is important as previous chemical methods are often limited by a lack of diversity. It also allows us to see how the kinetic parameters of the enzyme catalysed reactions change dependent on the identity of the substrate, allowing us to better justify the currently proposed mechanism and to better direct attempts to improve the enzyme through mutagenesis experiments. Indeed, several mutagenesis experiments have also been performed in an attempt to producevariants of the enzyme that would have either an increased enzyme scope or better reactivity with currently known substrates, and this work is also detailed within this thesis.

The challenge of process design is to develop an economically viable processing plant and control system which can be operated safely, reliably and with an acceptable environmental impact. The controllability assessment of a process deals with the assessment of its dynamic performance and its ability to cope with disturbances and uncertainties. One of the characteristics which limits the achievable process and control performances, independent of the controller design, is the presence of inverse response behaviour in the process. A system subject to inverse response has its initial response in the opposite direction from its final steady state. In a given linear process, the inherent characteristic that causes initial inverse response is the presence of RHP zeros in its transfer function. In this work, qualitative and quantitative indexes are presented to assess the effect of inverse response characteristics in linear processes. However, most industrial processes are nonlinear, and linear models may not describe these industrial processes with sufficient rigour. One novel approach to detect the presence of RHP zeros in the nonlinear setting is proposed in this work: By globally linearizing the nonlinear system into a system linear in input-output sense by feedback, the nonlinear expressions of the zero dynamics are extracted. This work shows that the zero dynamics and the zeros are equivalent for linear systems. Also, by analysing the stability of these zero dynamics, the inverse response characteristics of the nonlinear system can be identified directly in the nonlinear setting. Lyapunov's Second Method, and in particular Krasovskii's method, is employed to determine the stability characteristics of the zero dynamics. However, due to limitations associated with these stability tests, the zero dynamics may have to be linearized in order to fully quantify the inverse response characteristics of the nonlinear system. The proposed methodology is applied to two examples of Single Input Single Output systems, an industrial evaporator and an isothermal CSTR, and will be extended to the model of a Multi Input Multi Output non-isothermal CSTR with second-order kinetics. Throughout these examples, the methodology identifies which system is not affected by inverse response, and which system is. And for these systems, the effect of the inverse response in the nonlinear system is quantified over the given operating range.

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No description available.

A method of fault tree synthesis relevant to the generation of fault trees for use both in hazard assessment in the design of plant and in the analysis of fault conditions using a process control computer is described. List processing techniques and bit manipulation have been used to reduce computation time and computer storage require ments. The programming language used in the development of the algorithm was RTL/2. Several examples are presented to illustrate the methodology.

No description available.

The dehydration behaviour of several crystalline materials has been investigated, by means of lab-based studies, using X-ray diffraction and Differential Scanning . Calorimetry, and molecular modelling techniques. A review of several groups of materials, namely sugars, amino acids, and pharmaceutically important materials was undertaken. This showed how difficult it is to make predictions about dehydration behaviour based solely on examination of the structure of hydrated forms. Few patterns could be seen, other than the size of the molecules is important in determining whether or not a material will form crystalline structures at all levels of hydration. Amino acids are largely affected by the nature of the side chains. The nature of the structure of some of the pharmaceuticals meant that the pattern of dehydration, and the means by which the water molecules left the structure was easy to predict. The dehydration characteristics of a-lactose monohydrate, citric acid monohydrate, and calcium sulphate dihydrate have been studied using experimental methods and molecular simulation methods. The kinetics of dehydration of a-lactose monohydrate and citrjc acid monohydrate have also been studied, using a cell 'designed for this study which enabled the progress of the phase change to be followed using X-ray diffraction. The morphologies of these materials were also investigated, and the surfaces of the hydrated forms studied in order'to establish whether or not there may be a preferential route by which water leaves the structure. For a-lactose monohydrate, a further study was undertaken to try to establish the cause of the tomahawk morphology seen when it is grown from solution. Whilst the results presented are not clear-cut, they do indicate that both polar effects and the presence of lactose in the crystailising solution both have an influence on the shape of the crystal.

A mesoscale Oscillatory Baffled Reactor (“mesoscale-OBR”) is a laboratory-scale reactor (5mm inner diameter) with a total volume of approximately 5.5mL containing equally spaced baffles. Due to its small volume, it is suitable as a platform technology for process screening or investigating reaction kinetics. Traditionally, these are conducted in batch; however, continous screening can be performed in the mesoscale-OBR, with flexible adjustment of the input and reduced reagent usage. In this project, continuous dynamic and “steady state” screening was demonstrated in the mesoscale-OBR. These techniques can be used to rapidly and logically obtain process data and kinetics of any liquid-liquid reactions. Exothermic reactions of several aldehydes (benzaldehyde, o-tolualdehyde, m-tolualdehyde and p-tolualdehyde) with n-butylamine to form imines were chosen as the case studies to demonstrate the ability of the mesoscale-OBR. Online FTIR was used to monitor reactions. The mesoscale-OBR exhibited a high degree of consistency in experimental results: the uncertainty in the rate constant for benzaldehyde and n-butylamine imination was three times lower than in a conventional batch beaker method. MATLAB was used to model reaction kinetics and validated using experimental data. Both experiments and modelling demonstrated that the rate constant for 1-butanamine, N-(phenylmethylene)-synthesis was 2.1 x 10-1mol-0.9L0.9s-1 with total reaction order of 1.9 (1.7 for benzaldehyde and 0.22 for n-butylamine). The process development time when using “dynamic screening” (i.e continuous variation of one of the input parameters) was reduced by 50% compared to batch screening using beakers. A higher area to volume ratio of the mesoscale-OBR (than the beaker) allowed exothermic reactions to be screened safely and quickly e.g. temperature for solvent free imination was at ~40oC in a jacketed mesoscale-OBR, whereas ~90oC (above the boiling point of n-butylamine) for a jacketed beaker. To passively improve the temperature distribution along the length of the reactor, the centrally baffled mesoscale-OBR was constructed inside a thermosyphon: the temperature difference along the reactor length at residence times of 60s and 90s was reduced to 2oC, rendering the reaction safer and more amenable to determination of exothermic reaction kinetic parameters.

No description available.