On the modeling of dynamics and operation of reactive distillation
The aim of the present project was to study the factors that affect gross scale reactive distillation behaviour and to set a useful framework for control system design of reactive distillation. A modification of an equilibrium model based on using elementary quantities instead of molar quantities was used for different steady state and dynamic simulations of reactive distillation. Furthermore, a control system design method for reactive distillation was proposed and tested. In the first part of the present study, the role of operating conditions in reactive distillation behaviour was investigated. It was found that the complex nature of reactive distillation make this kind of process susceptible to input and output multiplicity. Furthermore, it was found that such behaviour is triggered by operating conditions that create high internal flow rates, and it could be found for any column configuration for these examples. The second part of the project was devoted to the dynamics and control system design of reactive distillation. A method, modified from other well known ones, was proposed to systematise the control system design of reactive distillation. The use of control tools on a linearised model gave the most convenient control configurations. It was found that the consideration of the possible disturbances was fundamental for correct discrimination between control schemes. The method was also able to recognise that for the case study, a high conversion point of an output multiplicity was relatively easy to control. Dynamic simulations which were used to corroborate the analysis results gave a good correspondence between them. Moreover, the dynamic simulations showed that the interaction between the important measurements controllers (such as temperature controllers) and the controllers of the column conditions (for instance, level controllers) may be important. Therefore it is recommended to consider both of them during the control system design method. It is considered that the findings of the present project will help in the understanding and design of reactive distillation processes.