Systematic methods for selected problems in design of reaction systems

• Main Author: Samant, Ketan Dinkar
• Language: ENG
• Published: ScholarWorks@UMass Amherst 2000
• Subjects: Chemical engineering
• Online Access: https://scholarworks.umass.edu/dissertations/AAI9988841

Design of reaction systems is an important problem in conceptual process design. However, relatively little is available in form of a formal systematic approach to tackle this problem; the main reason being the diversity in the reaction systems and the underlying phenomena. In this dissertation, an attempt is made to identify a strategy for systematic design of reaction systems by considering selected problems. First, a systematic method is developed for the design of the prep olymerization stage of polycondensation processes. In this method, feasible flow sheets and operating conditions are synthesized, analyzed, and evaluated on the basis of the reactive phase behavior. This method offers an elegant alternative to design by repeated simulations of a cascade of stirred tank reactors. Then, systematic methods are developed for the design of extractive reaction processes. Single and multiple stage processes that combine chemical reactions with liquid-liquid phase separation are synthesized and are shown to offer significant improvements in yield, selectivity, and ease of separation. A geometric method, which tracks the fixed points of the composition profiles is developed for assessing the feasibility of multiple stage processes. A stirred cell model, which represents an open system with multicomponent mass transfer and thermodynamic non-idealities, is used to elucidate the effects of reaction kinetics and mass transfer on the performance of extractive reaction processes. These effects are expressed in terms of dimensionless Damköhler numbers. The desired values of the Damköhler numbers are used to guide the selection of phase attributes and reactor types. The stirred cell model is also used to study liquid-liquid phase transfer catalytic processes. Two classes of flow sheets are proposed for catalyst recovery and guidelines are developed for choosing the recovery scheme, phase attributes, catalyst, and organic solvent. Finally, for the design of agitated reactors, the effect of turbulent mixing on fast chemical reactions is studied. This understanding is used to develop methods for synthesis, simulation, and scale-up. From the common features of the systematic design methods for these seemingly different problems, an attempt is made to identify the underlying strategy. It is hoped that this strategy will become the guideline for future research in this area.