(8i) Controllability Studies for CO2 Post-Combustion Capture Processes with Amines

CO₂ is the major greenhouse gas that is widely condemned as the root cause of the global climate change. The emission of CO₂ from fossil fuel combustion and industry processes contribute 78% of total greenhouse gas emission due to the globally economic and population growth. Therefore, the continuous technology advancement for CO₂ capture are crucial to reduce global greenhouse gas emissions as well as global climate changes. Amine-based post combustion CO₂ capture process has a long application history and has been recognized as a mature technology for coal-based power plant. Many studies have been conducted to improve this technology, such as choosing better amine solvents, optimize the lean solvent inlet conditions, modification the typical process designs and so on. However, few of the reported studies addressed dynamic process upset issues during the real practice. In applications, the intake flow of waste CO₂ streams will most likely fluctuate a lot due to the peak and off-peak of operation loads, which may lead to significant upsets for the CO₂ capture process, and thus affect the process efficiency and product quality.

In this study, plant-wide steady-state and dynamic models of a CO₂ post-combustion capture process with monoethanolamine (MEA) and Methyl diethanolamine (MDEA) blended amines have been developed to study the operational flexibility and controllability under disturbances. Modeling and simulation results shows the flowrate and temperature of lean loading stream entering the absorber and stripper’s reboiler duty are critical factors for CO₂ absorption performance. Therefore, novel control strategies with these factors by using advanced process control (APC) are studied in this work, this could not only maintain the feasible operation of the system, but also improve the energy performance under disturbances. Final results show that the fluctuate of CO₂ removal efficiency is no more than 0.1%, while the inlet flow disturbances have at most 30% changes during this period. Better control strategies could save extra 7% energy from heat exchangers and 18% power from pumps, which significantly improve the stability and economic performance of the studied CO₂ capture process.