Considerable ongoing risk of condenser in-leakage exists at Otahuhu B (OTB) Power Station. The condenser cooling water used at OTB station is corrosive brackish water with exceedingly high sodium and chloride concentrations. Significant signs of corrosion inside the condenser have been found recently. In the event of condenser in-leakage, the salt contaminants in the cooling water will directly enter the Heat Recovery Steam Generator (HRSG) with the potential for significant and costly damage resulting in a long plant outage. A dynamic mathematical model was developed in the thesis to analyse the consequences of condenser in-leakage at OTB station. The analysis results show that the tolerance of the condenser to any leakage of cooling water is almost zero. Because the existing condensate monitoring system is not designed to detect contamination in this time frame, a new fast response system is required to detect condenser in-leakage immediately. A new dedicated fast response condensate monitoring system has been engineered and installed at OTB station as a part of the project scope. The new system dramatically reduces the response time to condenser in-leakage events. Critical instruments utilise multiple redundancy schemes to enhance the availability and reliability of the system. In addition, action level voting, timing, and alarming has been automated to assist operators in making correct decisions. The new condensate monitoring system is presently fully functional. The project has successfully achieved the objective of controlling the risk of condenser in-leakage events and minimising damage and negative effects on the plant.

Considerable ongoing risk of condenser in-leakage exists at Otahuhu B (OTB) Power Station. The condenser cooling water used at OTB station is corrosive brackish water with exceedingly high sodium and chloride concentrations. Significant signs of corrosion inside the condenser have been found recently. In the event of condenser in-leakage, the salt contaminants in the cooling water will directly enter the Heat Recovery Steam Generator (HRSG) with the potential for significant and costly damage resulting in a long plant outage. A dynamic mathematical model was developed in the thesis to analyse the consequences of condenser in-leakage at OTB station. The analysis results show that the tolerance of the condenser to any leakage of cooling water is almost zero. Because the existing condensate monitoring system is not designed to detect contamination in this time frame, a new fast response system is required to detect condenser in-leakage immediately. A new dedicated fast response condensate monitoring system has been engineered and installed at OTB station as a part of the project scope. The new system dramatically reduces the response time to condenser in-leakage events. Critical instruments utilise multiple redundancy schemes to enhance the availability and reliability of the system. In addition, action level voting, timing, and alarming has been automated to assist operators in making correct decisions. The new condensate monitoring system is presently fully functional. The project has successfully achieved the objective of controlling the risk of condenser in-leakage events and minimising damage and negative effects on the plant.

Considerable ongoing risk of condenser in-leakage exists at Otahuhu B (OTB) Power Station. The condenser cooling water used at OTB station is corrosive brackish water with exceedingly high sodium and chloride concentrations. Significant signs of corrosion inside the condenser have been found recently. In the event of condenser in-leakage, the salt contaminants in the cooling water will directly enter the Heat Recovery Steam Generator (HRSG) with the potential for significant and costly damage resulting in a long plant outage. A dynamic mathematical model was developed in the thesis to analyse the consequences of condenser in-leakage at OTB station. The analysis results show that the tolerance of the condenser to any leakage of cooling water is almost zero. Because the existing condensate monitoring system is not designed to detect contamination in this time frame, a new fast response system is required to detect condenser in-leakage immediately. A new dedicated fast response condensate monitoring system has been engineered and installed at OTB station as a part of the project scope. The new system dramatically reduces the response time to condenser in-leakage events. Critical instruments utilise multiple redundancy schemes to enhance the availability and reliability of the system. In addition, action level voting, timing, and alarming has been automated to assist operators in making correct decisions. The new condensate monitoring system is presently fully functional. The project has successfully achieved the objective of controlling the risk of condenser in-leakage events and minimising damage and negative effects on the plant.

Les légionelles sont un enjeu de santé publique majeur car ces bactéries sont responsables des cas de légionellose, parfois mortels. Les tours aéroréfrigérantes (TAR) peuvent être incriminées car pouvant potentiellement émettre des aérosols contaminés. Un traitement de désinfection de ces eaux est donc nécessaire. Cependant les techniques actuelles conduisent très souvent à des injections importantes de réactifs induisant des rejets écotoxiques dans l'environnement qu'il est nécessaire de limiter. L'application du traitement d'oxydation avancée H2O2/UV – considéré comme innovant pour ce domaine et dont l'impact environnemental est limité (décomposition du peroxyde d'hydrogène en eau et oxygène, peu de production de composés toxiques) – a prouvé son efficacité de désinfection à la fois au sein d'un pilote de laboratoire sur une eau reconstituée, chargée en microorganismes et matière organique, mais aussi lors du traitement de l'eau d'une TAR du secteur tertiaire. Les ultraviolets ont été appliqués de manière continue (10 à 22 J.cm-2 sur le pilote ; 2 à 7 J.cm-2 sur la TAR) avec le maintien d'un résiduel constant en peroxyde d'hydrogène (10 à 50 mg.L-1 sur le pilote ; 3 à 10 mg.L-1 sur la TAR). Sur le pilote de laboratoire, le traitement H2O2/UV a montré une efficacité supérieure à l'application des UV ou du peroxyde d'hydrogène seul. Des abattements plus importants sur les paramètres microbiologiques de l'eau et des biofilms (ATP, bactéries cultivables et totales) et une modification profonde de la matière organique (minéralisation) ont pu être observés. Il a ainsi été conservé les avantages de chaque technique (désinfection reconnue des UV et action bactéricide de H2O2), tout en limitant leurs inconvénients (absence de rémanence des UV, fortes concentrations nécessaires en H2O2) grâce à la génération de radicaux hydroxyles pouvant agir sur les microorganismes et la matière organique. L'étude sur une TAR a confirmé ces résultats et a montré de bonnes performances de désinfection en comparaison avec celles obtenues pour le dioxyde de chlore. Cependant, lors les phases d'optimisation des essais, une adaptation des bactéries au peroxyde d'hydrogène a été observée indiquant la nécessité d'un contrôle régulier de cet oxydant afin de maintenir un résiduel conséquent et d'éviter la mise en place d'une dérive du système. De plus, il a été montré que le traitement n'a eu qu'une faible action sur les produits de conditionnement de l'eau (antitartre, anticorrosion). Une rapide évaluation économique a permis de placer le couplage H2O2/UV dans le même ordre de grandeur que les traitements habituels. / Legionella is a major public health issue as they are responsible for Legionnaires' disease, which can be fatal. Cooling towers are often incriminated because of their potential emission of contaminated aerosols. A disinfection process for treating water is then necessary. However, current techniques often need high concentrations of chemical products which lead to ecotoxic releases into the environment. UV-H2O2 is an advanced oxidation process with a limited environmental impact (hydrogen peroxide decomposition into oxygen and water, low production of toxic compounds). It was shown that this method is an effective technique of disinfection both in a laboratory pilot on water charged with microorganisms and organic matter, and in the water treatment of a cooling tower (service sector). UV irradiation was applied continuously (10 – 22 J.cm-2 on the pilot; 2 – 7 J.cm-2 on the cooling tower) with a constant residual of hydrogen peroxide (10 to 50 mg.L-1 on the pilot; 3 to 10 mg.L-1 on the cooling tower). On the laboratory pilot, UV-H2O2 showed a higher efficacy than UV or hydrogen peroxide treatments applied alone. A more important reduction of microbiological parameters in water and biofilms (ATP, heterotrophic plate and total bacteria counts) and a deep change in organic matter (mineralization) were observed. The advantages of each process (both well-known UV disinfection and bactericidal action of H2O2) were selected by limiting their disadvantages (no residual with UV, need for high concentrations of H2O2) through the generation of hydroxyl radicals, acting on microorganisms and organic matter. The study on a cooling tower confirmed these results and showed good disinfection performances compared with those obtained for chlorine dioxide. However, the optimization phases of the treatment highlighted a bacterial adaptation to hydrogen peroxide. A monitoring of this oxidant is required in order to maintain a residual, and therefore to avoid a drift of the system. Besides, UV-H2O2 showed little effect on scale and corrosion inhibitors. A rapid economic assessment allowed to placing UV-H2O2 in the same order of magnitude as usual treatments.

Section 316(b) of the Clean Water Act requires thermal power generating facilities to minimize adverse environmental impact resulting from the operation of cooling water intake structures (CWIS). Adverse environmental impact can occur when aquatic organisms are impinged on traveling water screens. Modified traveling screens were developed to improve the post-impingement survival of organisms. These screens have been used at a few power plants and are now being considered at additional facilities to reduce the mortality of juvenile and adult fish. Existing biological efficacy data show that post-impingement survival is highly variable by species. The majority of previous installations are at estuarine facilities. As such, there is a lack of biological efficacy data with many of the freshwater species commonly impinged at CWIS. In addition, most of the existing modified screen installations were installed prior to 1990. Since that time, improvements in screen designs have increased survival. For these reasons, the existing biological efficacy of the new screen designs was limited and largely unknown for many freshwater species. The mortality, injury, and scale loss rates of 10 species of freshwater fish impinged and recovered with a modified traveling screen were evaluated in the laboratory. Species tested included: golden shiner (Notemigonus crysoleucas); fathead minnow (Pimephales promelas); white sucker (Catostomus commersoni); bigmouth buffalo (Ictiobus cyprinellus); channel catfish (Ictalurus punctatus); hybrid striped bass (Morone chrysops × M. saxatilis); bluegill (Lepomis macrochirus); largemouth bass (Micropterus salmoides); yellow perch (Perca flavescens); and freshwater drum (Aplodinotus grunniens). Fish were impinged at 0.3, 0.6, or 0.9 m•s-1 velocity. Mortality, injury, and scale loss rates were generally low. Mortality rates did not exceed 5% for any species and velocity tested, indicating that this technology has potential to substantially reduce impingement mortality at CWIS. Despite a general trend toward increasing mortality at higher velocities, velocity was only a significant factor in the mortality of bluegill (P=0.0005). Injury and scale loss rates were low for most species tested, although they were more variable than observed rates of mortality. There was a trend toward lower mortality, injury, and scale loss in larger fish. In all cases where fish length was a significant factor (P<0.05), the pattern of decreasing mortality, injury, and scale loss as fish increased in length was constantly observed. Additional tests were undertaken with channel catfish, fathead minnow, and golden shiner to assess the effect of duration of impingement on mortality, injury, and scale loss. Longer durations of impingement appeared to result in higher mortality, injury, and scale loss, especially at durations of impingement greater than 6 minutes. However, longer durations of impingement could be avoided at most cooling water intake structures by continuously rotating screens.

Neste trabalho, foi estudado o desempenho de um sistema constituído de torres de resfriamento e a sua integração em uma planta industrial de hidrogenação de butadieno. Caracterizou-se o desempenho das torres de resfriamento com base em um modelo fenomenológico, cujos parâmetros foram obtidos a partir da medição de variáveis operacionais reais. O processo de hidrogenação foi configurado em um simulador de processos, sendo o caso base estabelecido nas condições de projeto. Elaborou-se um módulo específico referente às torres de resfriamento, que foi integrado ao processo configurado no simulador. Em seguida, analisaram-se as interações das condições operacionais da torre de resfriamento no desempenho do processo industrial. / In the present work, the performance of a system composed of a cooling tower integrated in butadiene hydrogenation plant was studied. An experimental investigation was made to characterize the cooling towers based on a phenomenological model and in real process conditions. The hydrogenation process was configured on a process simulator and design specifications were considered as base case. A cooling tower module was developed and integrated to the process simulator. The interaction of the cooling tower system and the plant operation was investigated.

O segmento industrial é um grande usuário de água e, na maior parte das situações, está localizado junto a aglomerações urbanas, caracterizando situação de dificuldade na obtenção deste recurso para as suas operações. As fontes de água estão cada vez mais saturadas e os processos de tratamento mais sofisticados. O objetivo deste estudo foi avaliar a viabilidade técnico-econômica da implantação do tratamento eletromagnético para água de resfriamento em indústrias químicas, substituindo ou complementando o tratamento químico convencional. O texto descreve inicialmente os fundamentos do tratamento de água baseado na aplicação de campo eletromagnético e, em seguida, os efeitos do uso dessa tecnologia sobre custos anuais de resfriamento em um caso típico da indústria química. Neste estudo foi dada ênfase ao efeito sobre os custos anuais da menor adição de produtos químicos, redução na vazão de purga e de reposição de água, além da redução na frequência de limpeza dos equipamentos e redução da carga poluente nos efluentes líquidos. O estudo foi aplicado a uma torre de resfriamento industrial, para a qual foi elaborado um modelo matemático considerando as taxas de consumo e especificações de água de resfriamento, além de parâmetros do processo de tratamento de água convencional e eletromagnético. São apresentados resultados de um estudo de sensibilidade para diferentes cenários, em que são identificados os fatores com maior efeito sobre os custos. Além disso, na aplicação ao sistema proposto, são estimadas condições ótimas de operação, considerando os ciclos de concentração para os quais pode haver maior redução de custos. Utilizando-se o tratamento eletromagnético para a água de resfriamento, há uma economia significativa, pois o número de paradas para a manutenção dos equipamentos pode ser reduzido. Dessa forma, o produto final do trabalho constitui-se em uma estrutura de cálculo voltada à estimação de custo do tratamento físico de água de resfriamento, o qual pode ser aplicado a diferentes cenários e condições de operação industrial. / The industrial sector is a major water user and in most situations is located next to urban areas, in a situation of increasing difficulty in collecting and treating water resources for its operations. The water sources are becoming more saturated and thus demanding more sophisticated treatment processes. The aim of this study was to evaluate the technical and economic feasibility of the implementation of electromagnetic treatment of cooling water in chemical industries, thus replacing or complementing the conventional chemical treatment. The text initially describes the principles of the physical process for water treatment based on the application of an electromagnetic field, and then focuses on the effects of the use of this technology on the annual costs of cooling in a typical case of the chemical industry. The study is focused on the effects of the electromagnetic treatment on the annual cost of cooling in view of the reduced consumption of chemicals, as well as reduction in purge flow and water replacement, reduced frequency of equipment cleaning, and reduction of pollution load caused by wastewater. The study results were applied to an industrial cooling tower for which a mathematical model was developed by considering consumption rates and cooling water specifications, as well as parameters of the electromagnetic and conventional water treatment processes. A sensitivity study was carried out for different scenarios, in which the most important factors affecting the annual cost are identified, and optimal process conditions are estimated for maximum concentration cycles. The study shows that the use of electromagnetic treatment for cooling water results in significant savings due to the reduced number of maintenance periods. The final product of this study is a calculation structure for cost estimation related to the physical treatment of cooling water, which can be applied to different scenarios and industrial operation conditions.

Neste trabalho, foi estudado o desempenho de um sistema constituído de torres de resfriamento e a sua integração em uma planta industrial de hidrogenação de butadieno. Caracterizou-se o desempenho das torres de resfriamento com base em um modelo fenomenológico, cujos parâmetros foram obtidos a partir da medição de variáveis operacionais reais. O processo de hidrogenação foi configurado em um simulador de processos, sendo o caso base estabelecido nas condições de projeto. Elaborou-se um módulo específico referente às torres de resfriamento, que foi integrado ao processo configurado no simulador. Em seguida, analisaram-se as interações das condições operacionais da torre de resfriamento no desempenho do processo industrial. / In the present work, the performance of a system composed of a cooling tower integrated in butadiene hydrogenation plant was studied. An experimental investigation was made to characterize the cooling towers based on a phenomenological model and in real process conditions. The hydrogenation process was configured on a process simulator and design specifications were considered as base case. A cooling tower module was developed and integrated to the process simulator. The interaction of the cooling tower system and the plant operation was investigated.

O segmento industrial é um grande usuário de água e, na maior parte das situações, está localizado junto a aglomerações urbanas, caracterizando situação de dificuldade na obtenção deste recurso para as suas operações. As fontes de água estão cada vez mais saturadas e os processos de tratamento mais sofisticados. O objetivo deste estudo foi avaliar a viabilidade técnico-econômica da implantação do tratamento eletromagnético para água de resfriamento em indústrias químicas, substituindo ou complementando o tratamento químico convencional. O texto descreve inicialmente os fundamentos do tratamento de água baseado na aplicação de campo eletromagnético e, em seguida, os efeitos do uso dessa tecnologia sobre custos anuais de resfriamento em um caso típico da indústria química. Neste estudo foi dada ênfase ao efeito sobre os custos anuais da menor adição de produtos químicos, redução na vazão de purga e de reposição de água, além da redução na frequência de limpeza dos equipamentos e redução da carga poluente nos efluentes líquidos. O estudo foi aplicado a uma torre de resfriamento industrial, para a qual foi elaborado um modelo matemático considerando as taxas de consumo e especificações de água de resfriamento, além de parâmetros do processo de tratamento de água convencional e eletromagnético. São apresentados resultados de um estudo de sensibilidade para diferentes cenários, em que são identificados os fatores com maior efeito sobre os custos. Além disso, na aplicação ao sistema proposto, são estimadas condições ótimas de operação, considerando os ciclos de concentração para os quais pode haver maior redução de custos. Utilizando-se o tratamento eletromagnético para a água de resfriamento, há uma economia significativa, pois o número de paradas para a manutenção dos equipamentos pode ser reduzido. Dessa forma, o produto final do trabalho constitui-se em uma estrutura de cálculo voltada à estimação de custo do tratamento físico de água de resfriamento, o qual pode ser aplicado a diferentes cenários e condições de operação industrial. / The industrial sector is a major water user and in most situations is located next to urban areas, in a situation of increasing difficulty in collecting and treating water resources for its operations. The water sources are becoming more saturated and thus demanding more sophisticated treatment processes. The aim of this study was to evaluate the technical and economic feasibility of the implementation of electromagnetic treatment of cooling water in chemical industries, thus replacing or complementing the conventional chemical treatment. The text initially describes the principles of the physical process for water treatment based on the application of an electromagnetic field, and then focuses on the effects of the use of this technology on the annual costs of cooling in a typical case of the chemical industry. The study is focused on the effects of the electromagnetic treatment on the annual cost of cooling in view of the reduced consumption of chemicals, as well as reduction in purge flow and water replacement, reduced frequency of equipment cleaning, and reduction of pollution load caused by wastewater. The study results were applied to an industrial cooling tower for which a mathematical model was developed by considering consumption rates and cooling water specifications, as well as parameters of the electromagnetic and conventional water treatment processes. A sensitivity study was carried out for different scenarios, in which the most important factors affecting the annual cost are identified, and optimal process conditions are estimated for maximum concentration cycles. The study shows that the use of electromagnetic treatment for cooling water results in significant savings due to the reduced number of maintenance periods. The final product of this study is a calculation structure for cost estimation related to the physical treatment of cooling water, which can be applied to different scenarios and industrial operation conditions.

Komati Power Station has installed a membrane plant consisting of ultrafiltration, double pass reverse osmosis and continuous electro-deionisation to treat cooling tower blowdowns in order to produce demineralised water and to conduct sidestream chemistry control of the cooling water circuit. This plant has replaced the existing ion-exchange plant that was used for the production of demineralised water and thus serves to reduce the loading of mobile salts in the ash dam (90% reduction) by eliminating regeneration effluent from the ion-exchange plant. Due to oil contamination in the cooling water circuit (when oil from oil coolers leaks into the cooling water), the membrane plant was also designed to operate on raw water from either the Nooigdedacht or the Vygeboom Dam or a blend of both dams. This is considered to be an emergency intervention under abnormal conditions to prevent possible irreversible fouling of the membranes due to oil in the cooling water. The Nooigtedach Dam water contains high concentrations of organic matter and is also enriched with nutrients due to raw sewage influent into the Dam water. This poses a challenge with regard to treatment of the high fouling feed water on the membrane plant. Natural organic matter in water has the ability to foul reverse osmosis membranes. This adversely affects the operation of the reverse osmosis process. However, very little information is available regarding the fouling characteristics of natural organic material in the raw and cooling water at Komati Power Station for the reverse osmosis membranes. Therefore, a pilot study was undertaken to determine the influence of natural organic matter on membrane fouling, to optimise the process for the removal of natural organic matter and to assess the ability of two different reverse osmosis membranes to effectively treat the high fouling feed water at Komati Power Station. The ability of a polyethersulphone hollow-fibre ultrafiltration membrane system was first evaluated to remove natural organic matter in the feedwater, by conducting pilot tests, initially without coagulation of the raw water and thereafter with in-line coagulation for organics removal. Jar tests were conducted in the laboratory to determine the most suitable coagulant and dosage for turbidity and natural organic matter removal. Various coagulants were tested and, based on the results of the jar tests, a coagulant (U3000) was identified based on optimal removal of both total organic carbon and turbidity at a dosing level of 20 mg/L. During the operation of the ultrafiltration pilot plant, permeate flow; feed pressure and feed temperature were monitored. Performance of the ultrafiltration membrane was monitored in terms of flux versus time for operation with and without a coagulation process. The results indicated that there was very little total organic carbon removal (maximum removal of 4%) without coagulation and a slight decrease in flux. The flux declined as a result of fouling but could be recovered by performing hydraulic backwashes and CEB procedures. Permeate flux, however, could be maintained at about 90 Lmh (from 642 hours of operation). Since most of the organics passed through the ultrafiltration membrane, it was concluded that the loss in flux was due to colloidal fouling of the membrane. This was observed when the operation was carried out using raw water as feed as well as when cooling water was used. The total organic carbon removal increased to 30% when the plant was operated with inline coagulation. The flux remained relatively stable during the first 600 hours of operation and only decreased significantly during the last 200 hours of operation as a result of fouling. The reduction in flux prior to cleaning was less than the 15% (maximum flux decline of 9.9% during the test period) which is acceptable according to the industry norm of 15%. It appeared that flux could be maintained at around 90 Lmh which was about the same as when no coagulant was applied. The 30% total organic carbon reduction that was obtained was not sufficient to reduce the organics to the level of 6mg/L dissolved organic carbon that was specified by the membrane manufacturer for the standard brackish water reverse osmosis membrane. Two reverse osmosis membranes – the standard brackish water reverse osmosis membrane (BW30-2540) and the extra-low-fouling membrane (BW30XFR-2540) – were assessed in terms of their ability to remove dissolved organic carbon, ease of cleaning of the membrane and the ability to recover flux after cleaning. This was done to establish which membrane is more suited to Komati’s high-fouling feedwater. The evaluation of the performance of the two reverse osmosis membranes was conducted using pre-treated water (filtered water after in-line coagulation, anti-scalant and biocide dosing) as well as using water that was not pre-treated. During operation (under both conditions), the normalised permeate flux, conductivity, dissolved organic carbon and organics absorbing at UV254 were monitored. It was established that in terms of flux decline that the extra low-fouling membrane gave slightly superior performance to that of the standard membrane, achieving longer production runs (up to 5 days compared with 3 days achieved by the standard brackish water membrane) without requiring chemical cleaning. The low fouling membrane achieved better CWF recovery after the cleaning cycles (81.26% Lmh of the virgin membrane on the occasions when there was flux loss) compared to the standard membrane (restored to 77.35% of CWF of the virgin membrane) when using untreated feed water. This performance improved when pre-treated feed water was used and the low fouling membrane’s CWF regained after the CIP was 95.89% which was within the industry norm of a flux recovery of 95%, indicating that the CIP had been effective. It was determined that the TOC rejection of the low-fouling membrane was higher (average TOC rejection of 97%, maximum TOC rejection of 99%) than that of the standard membrane (average TOC rejection of 95.3%, maximum TOC rejection of 97%). Preliminary efforts to optimize the pre-treatment for organics removal in order to reduce organic loading for the RO membranes confirmed that the use of granular activated carbon and use of an organic scavenger resin might not be economically feasible due to the relatively quick TOC breakthrough (8910BV, approximately 18000BV and less than 18000BV for the Filtrasorb 300, Filtrasorb 400 and organic scavenger resin, respectively). Although further investigations should still be conducted, the preliminary results indicate that it would be beneficial to also identify other options that can be further investigated for optimization of organics removal at Komati Power Station. Decline in the normalised flux as well as the evidence of biofouling were witnessed during the pilot operation suggesting that the membranes were fouled. Autopsies were performed on both membranes to identify foulants responsible for the decline in flux that was observed during the pilot study. The results did not indicate an organic foulant on the membrane surface. Biofouling should however, be monitored in the main plant as this was suspected to have resulted in the flux decline during the pilot study. The low fouling membrane demonstrated a better capability to treat the Komati raw and cooling water and would be expected to achieve lower operating costs for the plant (CIP costs and membrane replacement costs) while achieving better organics removal and it is therefore recommended that the low-fouling membranes be used at Komati Power Station as they are superior to the standard membrane and the cost of the low-fouling membranes is comparable to that of the standard membrane. While this would provide somewhat better performance than that obtained with the standard brackish water membranes, it is proposed that further investigation into pre-treatment optimization for organics removal as well as more efficient cleaning solutions be investigated to improve the performance and economics of the main water treatment plant at Komati power Station. / Dissertation (MSc)--University of Pretoria, 2013. / gm2014 / Chemical Engineering / unrestricted