Robust economic MPC of the absorption column in post-combustion carbon capture through zone tracking

Abstract

Several studies have reported the importance of optimally operating the absorption column in a post-combustion CO 2 capture (PCC) plant. It has been demonstrated in our previous work how economic Model Predictive Control (EMPC) has a great potential to improve the operation of the PCC plant. However, the use of a general economic objective such as maximizing the absorption efficiency of the column can cause EMPC to drive the state of the system close to the constraints. This may often than not lead to solvent overcirculation and flooding which are undesirable. In this work, we present an EMPC with zone tracking algorithm as an effective means to address this problem. The proposed control algorithm incorporates a zone tracking objective and an economic objective to form a multi-objective optimal control problem. To ensure that the zone tracking objective is achieved in the presence of model uncertainties and time-varying flue gas flow rate, we propose a method to modify the original target zone with a control invariant set. The zone modification method combines both ellipsoidal control invariant set techniques and a back-off strategy. The use of ellipsoidal control invariant sets ensure that the method is applicable to large scale systems such as the absorption column. We present several simulation case studies that demonstrate the effectiveness and applicability of the proposed control algorithm to the absorption column in a post-combustion CO 2 capture plant.

Economic model predictive control of integrated energy systems: A multi-time-scale framework

“…However, little attention has been given to a design of short-term or coordinated control strategies for large-scale complex nonlinear IESs. Additionally, the applications of centralized economic MPC (EMPC) in energy systems have been reported in [8], [49], which developed a new control strategy for coal-fired power plant and post-combustion carbon capture process, respectively. We note that EMPC of great ability to simultaneously handle optimization and tracking problems is in advance of conventional hierarchical control schemes, which is highly appropriate for IESs coordinated control problem.…”