Transient Behavior of a Post Combustion CO2 Capture Process

Övrigt konferensbidrag, 2013

Modeling of the dynamic behavior of post-combustion CO2 capture process and subsequent integration with power cycles and industrial processes is a topic which currently is gaining increasing interest. The transient behavior of the CO2 absorber and the solvent regenerator with respect to liquid to gas flow rates, capture rates and heat requirements need to be controlled while, at the same time, the operation of the capture unit must comply with the operation and control of the power plant. Also, the importance of control strategies for dynamic operation increases in base load thermal power plants when the requirements for load flexibility increase, e.g. as a result of more wind power and other intermittent power sources in the energy system. Furthermore, the capture cycle may also be used to reduce the load variation of the power plant by storing CO2 rich solvent during peak demand, which then may be regenerated during periods of low demand [1]. Numerous steady-state analyses of the post-combustion capture process with MEA have been published (see e.g. Wang et al.[2] and the references therein), however less work has been carried out focusing on the dynamic behavior of the process. Kvamsdal et al. [3] presented a study of transient behavior of the absorption column in the capture system with respect to capture efficiency, liquid-to-gas (L/G) ratio and solvent loading during start-up and load reduction. The study includes cases with no process control as well as capture efficiency control. Lawal et al. [4] applied a rate-based dynamic model of the complete capture process. Different cases of process disturbances were investigated, such as reduced reboiler duty and increased flue gas flow to the system, and the effects on the capture efficiency, solvent loading and heat requirement of the process were studied. The previous work mostly focuses on the transients observed in the capture system while the interactions and consequences for the connected processes, the power plant/industrial process and the CO2 transportation network respectively, are rarely discussed. This work includes the capture process and the connection to a power plant process with the aim to evaluate the transient behavior of the capture system with respect to typical load-change ramp rates in modern coal power plants as well as to discuss the consequences for the steam cycle and the CO2 transportation network connected to the capture system.