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This thesis examines theoretically the potential of the plasma confinement device known as a Stellarator as a fusion reactor. Chapter one contains a survey of the requirements for nuclear fusion to take place in a device employing magnetic confincment. The range of reactor parameters which are appropriate is- derived, both from the point of view of plasma physics and on the basis of a rather crude economic model. Chapter two begins with a discussion of the equilibrium of plasma in Stellarators. Solutions of the equilibrium equations are obtained, employing an Inverse aspect ratio axpansicn of the field quantities. Chapter three Indicates which macroscopic" instabilities are cause for concern in Stellarators without net longitudinal currant. A. stability criterion appropriate to Stellarators is evaluated, using the equilibrium fields found in the proceeding chapter. Chapter four is devoted to the study of the effects of particles which are localised in the ripple of the Stellarator masnetic field on transport. A random walk theory of their contribution to diffusion is given. Chapter five contains a description of the coil systems capable of generating fitellarator fields, and their properties. Specialising to "twisted" coils, geometrical scaling laws are sought, which describe the properties of the fields they produce. Chapter six is a brief indication as to how such coils may be incorporated into a reactor. Chapter seven considers the parameters of a Stellarator reactor based on "twisted" coils, and shows how they may be written in terms of the raajor and minor radii of the device. An economic model of the reactor is given, which allows us to optimise the reactor, to obtain the cheapest system at fixed total power output and wall loading. The result is shown Co be considerably less expensive than similar Tokamak designs.

Master of Science in Engineering - Engineering / The employment of an electrochemical process is an attractive alternative for the treatment of effluents. When dealing with solutions of low metal ion concentrations mass transport limitations are significant and large electrode surfaces are required. The use of a reactor containing a three-dimensional electrode is preferable as the surface area per unit volume is orders of magnitude greater than that of the familiar plate type reactor. A benchscale electrochemical reactor was designed and constructed to incorporate a cylindrical packed bed cathode. The flow of electrolyte is perpendicular to the direction of the flow of the current and the system is operated galvanostatically in a batch recirculation mode. The industrial stream selected for examination contains palladium and copper ions and a small concentration of platinum in a chloride medium containing ammines. The evolution of chlorine gas at the anode by the oxidation of the chloride ions is prevented by the inclusion of a cation exchange membrane and a separate anolyte, namely sulphuric acid, is introduced to the outer anodic chamber. Tests were conducted on both synthetic and industrial solutions and a simplified model which was derived was used to estimate the mass transfer coefficients. The concentrations of the palladium, copper and platinum in the plant effluent were approximately 150, 200 and 10 ppm respectively. The results show that the metal ions can be rapidly reduced to well below 1 ppm in each case. The separation of the palladium and copper ions is shown to occur to a limited degree during electrodeposition, with the extent of separation increasing for lower current densities. Enhanced separation may be possible during the removal of the deposited metals from the cathode either by anodic stripping or chemical treatment. A further method for the recovery of the metals is the combustion of the graphite particles. The high value of palladium, coupled with the significant recoveries shown to be achievable, suggest economic viability in addition to the environmental benefits.

A dissertation submitted to the Faculty of Engineering and the Built Environment, University of the Witwatersrand, in fulfilment of the requirements for the degree of Master of Science in Engineering. Johannesburg, 2016 / Traditional work in batch processes has focused mainly on the optimisation of batch reactors and the scheduling of batch processes. Recent development in the application of attainable region (AR) theory has allowed for its entry into this landscape. As time is a crucial consideration in the study of these systems, furthering the application of AR theory to batch reactors required the incorporation of time into the ARs. This was previously done in terms of residence time for continuous systems. With its use in batch systems this work sought to investigate how the time component differs within ARs between batch and continuous systems. It demonstrated that while residence time could be undergo linear mixing, the time in batch systems could not due to its nature. Therefore the ARs generated in concentration-residence time and concentrationtime space would differ slightly. A way to circumnavigate this was proposed in that the AR be plotted in terms of concentration and residence time following which the continuous reactor structure is obtained. From this the batch structure can be determined by substituting the equivalent reactor types. Production rates were also introduced as a method of interpreting an AR plotted in concentration-residence time space. By minimising the time taken to reach a particular point in the AR, one may effectively increase the rate at which the desired product can be produced. The developed concepts were applied to two example systems with the aim of obtaining the batch reactor structure for the most productive point that satisfied a given objective. Success was achieved for 2D single reaction system as well as a more complex 3D two biological reaction system. The more complex system led to the development of non-conventional attainable regions in terms of another process variable; in this case pH was used to demonstrate the concept although other variables such as temperature and pressure may be used in a similar fashion. Such plots may be used to further optimise the reaction system or identify a particular region in which to operate. Further development of AR theory to batch reactors has indeed allowed its use in conjunction with optimisation and scheduling of batch processes. Most notably, scheduling may utilise the obtained batch structure as part of the process to be scheduled or use the indicated reaction time. / MT2016