Master of Science in Engineering by research: “A dissertation submitted to the Faculty of Engineering and Built Environment, University of the Witwatersrand, Johannesburg, in fulfillment of the requirements for the degree of Master of Science in Engineering.” Johannesburg, 05 February 2018 / In most industrial processes, energy is an integral part of the production process; therefore, energy consumption has become an intensified area in chemical engineering research. Extensive work has been done on energy optimisation in continuous operations; unlike in batch operations because it was believed that due to the small scale nature of batch plants, small amounts of energy is consumed. Certain industries such as the brewing and dairy industries have shown to be as energy intensive as continuous processes. It is, therefore, necessary for energy minimisation techniques to be developed specifically for batch processes in which the inherent features of batch operations such as time and scheduling are taken into account accordingly. This can be achieved through process integration techniques where energy consumption can be reduced while economic feasibility is still maintained. Most of the work done on energy minimisation either focuses on direct heat integration, where cold and hot units operating simultaneously are integrated, or indirect heat integration, where units are integrated with heat storage. The schedules used in these models are, in most cases, predetermined which leads to suboptimal results. This work is aimed at minimising energy consumption in multipurpose batch plants by using direct heat integration together with multiple heat storage vessels through mathematical programming. The proposed approach does not use a predetermined scheduling framework. The focus lies on the heat storage vessels and the optimal number of heat storage vessels together with their design parameters, namely size and the temperature at which the vessels are initially maintained, are determined. The formulation developed is in the form of a mixed integer non-linear program (MINLP) due to the presence of both continuous and integer variables, as well as non-linear constraints governing the problem. Two illustrative examples are applied to the formulation in which the optimal number of multiple heat storage vessels is not known beforehand. The results rendered from the model show a decrease in the external utilities, in the form of cooling water and steam, compared to the base case where no integration is considered and the case where only one heat storage vessel is used. / MT 2018

Mercury occurs naturally and as a result of human activities. One such activity is the combustion of mineral-enriched, sub-bituminous coal to produce electricityan industry that has existed for over 100 years. Although coal is absolutely necessary to supply the power that South Africa and its neighbouring countries requires, the emitted gases, especially mercury, impact the environment and present a complex array of health-related problems. Controlling the impact of mercury present in the environment depends on the efforts of governments, scientists, business and industry, agriculture, environmental organizations and individuals. Mercury is emitted from the point sources in different forms. Accurate determination of the emitted forms or species of mercury has become a global interest. Determination of the various mercury species requires several well-understood analytical techniques for the confident assessment of potentially contaminated samples. This study focuses on the development, validation and application of analytical methodologies that are capable of differentiating between the different forms of mercury in environmental samples (air, liquids and solids) from coal-fired power plants. Capillary electrophoresis with amperometric detection, high performance liquid chromatography with amperometric detection, and atomic fluorescence spectrometry methods were developed for mercury speciation. Very low detection limits observed using the methods. For capillary electrophoresis with amperometric detection, the detection limits were 0.005±0.002 μg/l for Hg2+ and 0.4±0.05 μg/l for MeHg+. Detection limits of 2±0.04 ppt and 0.01±0.02 μg/l for Hg2+ were observed for high performance liquid chromatography with amperometric detection and atomic fluorescence spectrometry respectively. These detection limits are attractive for the monitoring of mercury in the environment. Total mercury in solids (coal and ash) was measured by direct mercury measurement using a well-established method, involving the use of the mercury analyzer LECO AMA-254. Total gaseous mercury was measured using the Tekran 2537B system. On application to environmental samples, very good correlations in results were observed between the different methods. Mercury speciation in South African coal after acid extraction showed that only Hg2+ species was detected from the extracts and that 96% of total Hg in acid extracts is in the Hg2+ species form. Different trends in Hg speciation results at the Elandsfontein Air Quality Monitoring (AQM) station were observed over the sampling period. During winter sampling, Hg2+ was the predominant species, while Hg0 was predominant the species during summer sampling. Mercury speciation carried out at Duvha Power Station (units 1 and 2), equipped with fabric filter devices, revealed that the predominant form of Hg after the fabric filter devices was Hg2+, due to oxidation of Hg0 to Hg2+ as the flue gas temperature decreases. Mercury speciation at the Majuba Underground Coal Gasification flare revealed that although mercury is emitted from power plants in the form of different chemical species, with each species have a different fate in the atmosphere, the climate, wind direction and terrain also play roles in the transport of mercury emissions. Therefore, it is difficult to predict the transport patterns of emissions. Nonetheless, with correct measuring equipment and modelling, the patterns of emissions should be able to be predicted. The patterns observed and data recorded at the Elandsfontein AQM station and Duvha Power Station, respectively, were however, insufficient to permit accurate modelling. This study raised a number of other questions which are too comprehensive for this study to address. Therefore, more comprehensive atmospheric and combustion studies should be done.

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The objectives of this project are to show the feasibility of micro-hydropower and to provide adequate engineering data for those people who wish to design their own micro system. Nine case studies are reviewed and analyzed in an attempt to determine general design parameters. Comparative data for these studies comes from preliminary permit applications submitted to the Federal Energy Regulatory Commission. Information on such topics as flow measurements, heads, generators and turbine technology are presented. Duration curves are explained with examples using data from a river found in Colombia, South America. Finally, a preliminary design of a micro-hydro facility is calculated for implementation on a stream that is part of the Tennessee River Basin.

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Less Developed Countries (LDC's) now have a total of about 2.8 billion people, or approximately 70 percent of the total world population. World populations and current energy consumption are such that is all the world's countries came up to the U.S. per capita energy use, the world's consumption would multiply by a factor of seven. For the LDC's, energy development will be an increasingly important issue. Hydropower technology is on the shelf, and available now, of proven feasibility both technically and economically, and presents a sound and rational energy solution from the environmental viewpoint. It is a technology which could be useful to the Less Developed Countries for the long term, irrespective of the shift from abundant low-cost fossil fuel options or the development of more exotic alternate energy technologies. With its continuing replenishment and nondepleting characteristics, it remains one of the most attractive sources of energy. The nature of water resources includes a distributive element which makes it ideal for rural development. The apparent shift in development policy, from the traditional "top-down" industrialization approach to the "bottoms-up" reach the village approach, requires decentralized applications of energy resources attainable through development of hydropower in many regions of the world. Distributed Small Scale Hydropower (SSH) systems offer excellent opportunities to augment energy supplies to many rural areas. Also, in a modest way the development of a community infrastructure, training of operating and maintenance personnel, and initiation of small scale agribusiness enterprises may be undertaken. Each of these activities could result in relatively major contributions to the improvement of quality of life. SSH sites are found in abundancy in most mountainous regions and offer sensible possibilities for decentralized applications in LDC's.

The demand for electric energy increases every year. However, due to recent changes in the U.S. energy supplies, a growing gas shortage forced suppliers to curtail deliveries of natural gas for power generation. Many utilities anticipating supply problems switched to burning more costly light distillate oil. Unfortunately the Arab boycott of 1973 and the following price increases for oil forced again utilities to seek a cheaper source of fuel, namely coal, as a substitute for oil. Even though the U.S. has abundant supply in coal, the use of coal in power generation was limited in the past because of a higher capital cost associated with installing air pollution control devices. Therefore, current utilities primary concerns are "does the lower fuel price of the coal power plant really outweigh its disadvantage of higher construction costs as compared to the oil-burning power plant?". Thus, the purpose of this paper is to evaluate the economic preference of the coal burning power plant compared to the oil-burning power plant in suppling base load power. An extensive analytical model accounting for the effects of escalating fuel prices was examined and a computer simulation model was developed to handle risk associated with various input parameters using the SLAM as a simulation language.