Plantwide Control of CO2 Capture by Absorption and Stripping Using Monoethanolamine Solution

In this work, plantwide control of an absorption/stripping CO2 capture process using monoethanol-amine was investigated using dynamic simulation. In this system, CO2 removal ratio is influenced by operating variables such as lean solvent rate and lean solvent loading, which is in-turn determined by reboiler duty in the stripper. Moreover, we found that the long-term stability of the system cannot be achieved unless the water balance is properly maintained. Hence the following control structure was proposed. In this scheme, the CO2 removal target is guaranteed using the lean solvent feed rate to the top of the absorber column. The overall water inventory was maintained by controlling the liquid level in the reboiler of the stripping column using makeup water. In order to operate the process with an appropriate lean solvent loading, the temperature at the bottom of stripper is controlled by the reboiler duty. This control structure was tested by disturbances involving inlet flue gas flow, CO2 concentrations, and H2O concentrations as well as changes in removal targets. Dynamic simulations showed that the system can achieve removal targets and stabilize quickly while keeping optimum lean loading constant. To ensure minimum energy consumption, optimizing control can be carried out by adjusting the set point of the reboiler temperature.