Experimental results of transient testing at the amine plant at Technology Centre Mongstad: Open-loop responses and performance of decentralized control structures for load changes

The transient response of key process variables to changes in flue gas volumetric flow rate, solvent flow rate and reboiler duty were analyzed. In general the process stabilizes within 1 h for 20% step changes in process inputs, being the absorber column absorption rates the slowest process variable to stabilize to changes in reboiler duty and solvent flow rate. Tests on fast load changes (10%/min) in flue gas flow rate representing realistic load changes in an upstream power plant showed that decentralized control structures could be employed in order to bring the process to desired off-design steady-state operating conditions within (<60 min). However, oscillations and instabilities in absorption and desorption rates driven by interactions of the capture rate and stripper temperature feedback control loops can occur when the rich solvent flow rate is changed significantly and fast as a control action to reject the flue gas volumetric flow rate disturbance and keeping liquid to gas ratio or capture rate constant.