Investigation of control performance on an absorption/stripping system to remove CO2 achieving clean energy systems

Abstract

Control study is crucial to ensure smooth operation of any unit operation for clean energy system. There has been growing attention on the utilization of advanced model-based controllers in control studies for CO2 capture. However, such advanced controllers are expensive hence proper performance justifications are needed prior to investment. In the current study, both Proportional-Integral (PI) and Model Predictive Control (MPC) control strategies are investigated and implemented on a pilot scale natural gas CO2 absorption/ stripping system running at higher pressure as well as higher CO2 content, utilizing MATLAB/SIMULINK-Aspen Plus Dynamics interface. The novelty of the work is mainly on the investigation study between the efficiency of the standard PI and MPC controllers for a high pressure and high CO2 content pilot-scale CO2 absorption system. For such high pressure and high CO2 content system, it is imperative to evaluate whether special focus on the control strategy is needed or not. This work simulates and investigates the dynamic behavior and performances of PI and MPC controllers of a high-pressure absorption/stripping system. In addition, a second order model of the system has been developed, which is useful for future studies. Controller performance of the Proportional-Integral (PI) and Model Predictive Controller (MPC) are compared using the features of the responses as well as the residual error index i.e., Integral Absolute Error (IAE). The performance of the PID and MPC controllers based on set point tracking of both the controlled variables for 5% and 15% step changes have been evaluated. Compared to the PI controller, the MPC controller has no peak overshoots, i.e., it shows 10% and 2.86% lower error in the IAE index, and it is capable of handling interactions between the variables of the absorption/stripping system.