Design of Control Structure for Binary Distillation Column
Ramsagar VooradiSarath Babu Anne
National Institute of Technology,Department of Chemical Engineering
摘要：Design of control structure for distillation columns is an important aspect in order to minimize the damage caused due to unexpected disturbances. In this study, the dynamic simulation of a distillation column has been carried out using Aspen Dynamics. For the purpose of the present study, a binary mixture of propaneisobutane is selected. The distillation column has been first designed at steady state using DSTWU model, a shortcut design model in Aspen Plus. The design is fine-tuned and the column is sized with RADFRAC model, a rigorous rating model using the design data obtained from the DSTWU model. The steady state simulation has been exported to Aspen Dynamics under pressure driven simulation mode for carrying out dynamic simulation. The steady-state design parameters of the column are used as initial conditions for the dynamic simulation. The Dynamic simulation of the distillation column has been carried with three different processes, which are classified based on the control structure used as: Process-1 controls the composition of top product using the temperature controller; Process-2 controls the composition of top product using a composition controller and Process-3 controls the composition using a cascade of temperature and composition controllers. The tuning of different controllers has been performed using the Relay AutoTuning test, and the control parameters have been calculated using Tyreus-Luyben and Ziegler-Nicholas tuning rules. The dynamic response of the three processes mentioned above has been studied subjecting them to various disturbances. The major conclusions drawn from this study are: The temperature controller alone（ProcessI） is not suitable to control both top and bottom product compositions, when the step disturbance in feed composition is given. Though the composition controller（Process-Ⅱ） is able to maintain the desired compositions of the top and bottom products, the response of the system is very poor. The response has been observed to be fast and without any oscillations in case of Process-Ⅲ when compared to both Process-Ⅰ and Process-Ⅱ.
International Conference on Chemical, Civil and Environmental Engineering （ICCCEE’2015, UK）