Plantwide control of CO2 capture by absorption and stripping using monoethanolamine solution

In this study, plantwide control of an absorption/stripping CO₂ capture process using mono-ethanolamine 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, 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 liquid level in reboiler of the stripping column using makeup water. In order to operate process with an appropriate lean solvent loading, the temperature at the bottom of stripper is controlled by reboiler duty. This control structure was tested by disturbances involving inlet flue gas flow, and CO₂ concentrations. Dynamic simulations showed that system can achieve removal targets, stabilize quickly while keeping optimum lean loading constant. To ensure minimum energy consumption, optimizing control can be carried out by adjusting the setpoint of reboiler temperature.