Design of operable reactive distillation columns.

摘要

Reactive distillation is an integrated process which considers simultaneousudphysical and chemical transformations. It is increasingly receiving attentionudboth from industry and academia. Significant advances have been made inudthe area of modelling and simulation as well as the implementation of suchudunits industrially. However, the area of control and optimisation of suchudunits has not been explored thoroughly.udThe thesis presents a general framework for simulation and design, which canudhandle reactive and non-reactive systems. Various different aspects of theudmodelling and simulation of distillation have been described in order to understandudthe behaviour of the reactive distillation columns. In the frameworkudboth simulation modes, steady-state and dynamic, are considered and theudprocess is described by equilibrium and non equilibrium-based models. In audrate-based (or non equilibrium) model, mass transfer rates between liquid andudvapour phase are considered explicitly, based on the Maxwell-Stefan equations.udEquilibrium is attained at the phase interface in the non-equilibriumudmodel. A switching policy makes it possible to go from one model to theudother, based on the knowledge gained, by following the Gibbs free energy asuda function of time. Tray efficiency has also helped in determining the switchudbetween the non-equilibrium and equilibrium models, and has been studiedudfor various systems.udThe existence of multiple steady state has been verified through simulationudwith the hybrid model. Bifurcation diagrams also confirmed the existence ofudoutput multiplicity obtained in the simulations.udAnalysis of process controllability at the design stage has been shown to provideudguidance for improving process operation. In the thesis controllabilityudmeasures for the reactive systems studied are presented as a first step towardsudcontrol structure selection.udA method for obtaining the design of reactive separation columns at minimumudtotal annualised cost (investment and operating costs) and which willudbe able to maintain stable operation in the presence of variability is alsoudpresented.