Dynamics and Regulatory Control of Biodiesel Purity from a Reactive Distillation Process

Abstract – The open loop and disturbance rejection (regulatory) closed loop dynamic simulation of a reactive distillation process used for the production of biodiesel, details of which are given in the work of Giwa et al. (2015a), have been carried out in this work. The first-order-plus-dead-time transfer function model of the system used was developed with the aid of System Identification Toolbox of MATLAB. The input and output variables of the process were the reboiler duty of the column and the mole fraction of biodiesel obtained from the bottom section of the column, respectively while the disturbance variable was the reflux ratio. Both the open loop and the closed loop simulations of the system were achieved from the Simulink model of the system developed and run via written m-file codes. The results obtained from the open loop dynamic simulation of the process revealed that the disturbance variable had effects on the output (biodiesel mole fraction obtained from the bottom section) of the process because the steps applied to it made the output not to be at the desired set point. Furthermore, the application of P, PI and PID controllers tuned with Cohen-Coon and Ziegler-Nichols techniques showed that the process could be made to behave in a desired manner. However, the response given by the simulation of the system with P-only controller was found not to settle at the desired set-point value, while the simulations with PI and PID wer