Dynamic model and control system of carbon dioxide capture process in fluidized bed using computational fluid dynamics

Nowadays, the concentration of greenhouse gases in the atmosphere has been growing continuously due to the increase of energy consumption, generated from carbon-based fuels and has created global warming. In this study, a model of carbon dioxide capture adsorption in a fluidized bed reactor was developed based on experimental data using commercial CFD program called ANSYS FLUENT. Then the model was employed to observe the hydrodynamics behavior and the dynamic responses of CO2 capture inside the adsorber when the operating variables were changed. The effects of operating variables on carbon dioxide capture were evaluated. From the simulation results, both the inlet gas velocity and the inlet solid circulation rate affected the carbon dioxide capture. The relationships between inlet gas velocity and inlet solid circulation rate to the percentage of carbon dioxide capture were investigated and analyzed by using system identification toolbox in MATLAB. After that, these relationships were used to design a control system. For the considered control system, the inlet solid circulation rate was selected to be a manipulated variable, while the inlet gas velocity, composition and temperature were designated as system disturbances. The controlled variable was carbon dioxide content remaining in the flue gas at the outlet. It was found that the control system could maintain the concentration of carbon dioxide in the flue gas at a specified value.