Robust Optimization of a Post-combustion CO2 Capture Absorber Column under Process Uncertainty

Abstract

In recent years, greenhouse gas (GHG) emissions is a global concern due to high concentrations of these gases in the atmosphere. Carbon capture and storage (CCS) has been suggested as an attractive alternative to curb intensive CO2 emissions and reduce its impact to the environment. CCS technologies provide a direct alternative to reducing the emissions from coal and gas-fired power generation plants. However, in order to implement commercial-scale CO2 capture plants, further studies are needed to mitigate all possible costs of this technology such as high energy consumption. This work presents a study on a robust design optimization framework for a pilot-scale absorber column in post-combustion CO2 capture. A mechanistic model describing the behaviour of a post-combustion CO2 absorber column is explicitly considered. The proposed formulation takes into account uncertainty that will impact the absorber column due to seasonal or unexpected changes in the operating policies of a fossil-fired power plant, e.g., changes in the flue gas stream, as well as uncertainty associated with the physical thermodynamic properties of the species involved in the absorption process. Furthermore, in addition to the presence of model uncertainty, a multi-objective optimization in a multi-period scenario explicitly describing year-long seasonal changes in flue gas has been considered. Different scenarios were assessed in order to evaluate the impact of uncertainty and multi-period changes on the optimal multi-objective process design. Optimal design specifications between different number of uncertain realizations and periodical changes were studied. However, higher computational demands were observed under extensive evaluations of uncertainty. Results from this study suggest that larger dimensions in design are required when the optimization was evaluated under uncertainty and under multi-periods scenarios considering uncertainty. The results show that the optimal design considering uncertainty and seasonal changes will be able to comply with the CO2 capture policies. Thus, post-combustion CO2 capture systems must be designed under these conditions to ensure feasibility of these plants during operation.