Optimal design and operation of reactive distillation systems based on a superstructure methodology

A novel methodology for the simultaneous optimisation of design and operation of a complex reactive distillation process, considering a number of process alternatives (e.g. pre-/side-reactor, side-stripper, additional columns etc.), is presented. The methodology is based on a superstructure approach, and a detailed cost-based objective function, solved by MINLP optimisation. The methodology is illustrated using different case studies of industrial interest with varying separation and reaction characteristics. For easy separations, in terms of relative volatilities and boiling points order, a single reactive distillation column is found to be optimal for both fast and slower kinetics. However, when the separation is more challenging (i.e. product is a middle-boiler), the design is more complex, even for fast kinetics, and additional processing units, such as a pre-reactor and/or additional distillation columns, are required to meet the product quality specifications. It is found that the design, i.e. the capital cost, mainly depends on the relative boiling point rankings. For operation, chemical reaction equilibrium is the dominant factor. It is demonstrated, however, that the combined effects of separation and reaction must be considered carefully when designing a reactive distillation process. The liquid holdup has an impact on the reaction performance, and proper choice of holdup can lead to a more flexible design, able to mitigate production failure issues even for slower reactions

Applications of Aerosol Technologies in the Silicon Industry

In this dissertation, the focus was on two unit operations that have the potential to significantly lower the cost and energy required for refining silicon. First, the removal of carbon from silicon kerf (sawing dust from wafering) was examined to enable its recycling. Second, silane pyrolysis was studied to better understand the dynamics of the initial stages of silicon aerosol formation and growth

Microwave-assisted pyrolysis for biomass recovery and applications

A pressing environmental concern, agricultural waste demands sustainable solutions. This study explores converting agro-industrial waste into energy and innovative applications through microwave-assisted pyrolysis. It assesses waste-to-energy potential and introduces novel electrochemical sensors for biomedical and nitrite detection

Catalytic Transfer Hydrogenation Reactions of Lipids

Catalytic transfer hydrogenation (CTH) of lipids was investigated using 2-propanol as hydrogen donor for producing liquid hydrocarbons, e.g. jet fuels. The main sources of lipids selected in this study were waste cooking oil (WCO) and oil-laden algae-derived biofuel intermediate (BI). Two different catalysts were employed in this study, namely activated carbon and trimetallic-doped zeolite. The CTH reaction was between WCO and 2-propanol in a continuous flow reactor over a packed-bed activated carbon at near atmospheric pressure. Results revealed a high level of alkenes and aromatics compounds, which are not stable and are not environmentally unfriendly. To reduce these compounds in the liquid fuel, trimetallic catalyst was prepared and the reaction was by optimizing the reaction variables (temperature, pressure, weight hourly space velocity, and oil-2-propanol ratio). Results from the second study were better than that of the first, as the level of aromatics and alkenes was lower in the second study. However, the amount of branched and cyclo-alkanes (high octane rating compounds) was insignificant. Lipids from algae-derived oil-laden BI were extracted by 2-propanol and without evaporation of alcohol; the pregnant 2-propanol was subjected to CTH over the prepared trimetallic catalyst in a batch reactor. The liquid fuel product from this third study produced significant branched and cyclo-alkanes (serendipity). Finally, technoeconomic analysis (TEA) and life cycle assessment (LCA) of CTH reaction were conducted. The results were compared, with a conventional hydroprocessed renewable jet fuels (HRJ) process. Results showed that the economic performance of CTH was lower than that of HRJ, due to the large volume of 2-propanol employed in the CTH. However, the environmental performance of CTH was very impressive, compared to that of HRJ. Chapter 1 of this study describes the rationale for selecting WCO and 2-propanol as the potential hydrogen donor. In Chapter 2, 2-propanol was used the react with waste cooking oil by considering four reaction parameters: temperature, oil flow rate, WHSV, and pressure. Finally, the kinetics of the reaction were ascertained, in order to estimate reaction order, activation energy, and kinetic rate constant. Chapter 3 employed commercial catalyst doped with transition metals which catalyzed the reaction between waste cooking oil and 2-propanol. Optimization of the reaction was studied by varying temperature, WHSV, pressure, and oil-2-propanol ratio. The percent of transition metal employed remained constant. Chapter 4, on the other hand, explored the possibility of using oil-laden biofuel intermediate from flash hydrolyzed algae. The purpose was to utilize 2-propanol as oil extract and hydrogen donor in CTH reaction of the oil. Finally, Chapter 5 thoroughly discussed the technoeconomic and environmental performance of the CTH reaction of waste cooking oil and 2-propanol

Industrial hygiene characterization of photovoltaic solar cell industry

"Health and safety problems in the photovoltaics solar cell industry were evaluated. A comprehensive literature review and walk-through surveys of 14 production or research and development facilities were conducted. The investigation revealed that the industry appears to be generally well controlled, especially in the area of single crystal silicon technology. Comprehensive industrial hygiene sampling indicated that most chemical exposures were well within the standards. Exposures to silver (7440224) during grid metallization in one facility and to arsenic (7440382) during gallium arsenide (1303000) wafer production in another facility exceeded standards. The authors conclude that the major potential problems relate to containment and accidental release of toxic materials. They recommend further research into the carcinogenic potential of arsenic, cadmium (7440439), selenium (7782492), and beryllium (7440417), all of which are used in this industry." - NIOSHTIC-2NIOSHTIC no. 0009422480-112.pdf?id=10.26616/NIOSHPUB801121980Contract-210-78-00591119