Dynamics and Control System Design for Biodiesel Transesterification Reactor

Abstract

The immiscibility of vegetable oil in methanol provides a mass transfer challenge in the early stages of Transesterification reaction in the production of biodiesel. It is of a great significance to design high-performance nonlinear controllers for efficient control of these nonlinear processes to achieve closed-loop system's stability and high performance of a biodiesel CSTR. A mathematical model capable of predicting the performance and behaviour of a CSTR has been developed and evaluated. In this work, a comprehensive design procedures based on model predictive control (MPC) have been proposed to efficiently deal with the design of gain-scheduled controllers, controller tuning, optimal controllers and time-varying for nonlinear systems. Since all the design procedures proposed in this work rely strongly on the process model, the first difficulty addressed in this paper is the identification of a relatively simple model of the nonlinear processes under study. The second major difficulty is the analysis of stability and performance for such models using nonlinear control theory of a robust control approach. In the current work, the nonlinear model is approximated by a nominal linear model combined with a mathematical description of model error (due to nonlinearity) to be referred to (in this work) as model uncertainty. The robust control theoretical tools developed are used for the design of gain-scheduled Proportional-Integral-Differential (PID) control and gain-scheduled Model Predictive Control (MPC) in which the MPC method achieves the steady-state optimal set-points of the biodiesel Transesterification reactor.

Modeling and Control of a Biodiesel Transesterification Reactor

“…Researches on the effects of process parameter aimed at establishing optimum reaction conditions for maximum and profitable biodiesel production include works on the effects of temperature and pressure [20]; methanol-oil molar ratio [21], mixing rate [18], catalyst type [16] [22] and optimization of reactor parameters by [23] and [24]. The reaction mechanism for the transesterification of used vegetable oil to biodiesel occurs via a series of three-stage reversible reaction scheme; as with reversible reactions, the reactions can proceed in either direction if not effectively controlled.…”

“…The values of the transfer functions of the measuring device and the final control element as given by Equations (19) and (20) are usually assumed as the transfer functions of these components of the closed loop do not change and have minimal effect on the system [27].…”