Dynamic Simulation of MEA Absorption Process for CO2 Capture from Power Plants
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A dynamic MEA absorption process model has been developed to study the operability of this process in a dynamic fashion and to develop a control strategy to maintain the operation of the MEA scrubbing CO2 capture process in the presence of the external perturbations that may arise from the transient operation of the power plant. The novelty in this work is that a mechanistic model based on the conservation laws of mass and energy have been developed for the complete MEA absorption process. The model developed in this work was implemented in gPROMS. The process response of the key output variables to changes in the key input process variables, i.e., the flue gas flow rate and the reboiler heat duty, are presented and discussed in this study. In order to represent the actual operation of a power plant, the dynamic response of the MEA absorption process to a sinusoidal change in the flue gas flow rate was also considered in the present analysis. The mechanistic dynamic model was applied to develop a basic feedback control strategy. The implementation of a control strategy was tested by changing the operating conditions for the flue gas flow rate. The controlled variables, i.e., the percentage of CO2 absorbed in the absorber column and the reboiler temperature, were maintained around their nominal set point values by manipulating the valve stem positions, which determine the lean solvent feed flow rate at the top of the absorber column, and the reboiler heat duty, respectively. For the sinusoidal test, the amplitude of the oscillations observed for the controlled variables was smaller than those observed for the open-loop tests. This is because the variability of the controlled variables was transferred to the manipulated variable in the closed loop. The mechanistic dynamic model developed in this process can be potentially used as a practical tool that can provide insight regarding the dynamic operation of MEA absorption process. The model developed in this work can also be used as a basis to develop other studies related to the operability, controllability and dynamic flexibility of this process.