Numerical simulations of CO2 absorption by MgO-based sorbent in a gas–solid fluidized bed

Abstract

Given that carbon dioxide (CO2) constitutes the predominant proportion of greenhouse gas emissions, its capture, utilization and storage have always been a subject of great concern. Gas-solid fluidized bed has become one of the commonly applied equipment for the removal of CO2 from flue gases owing to its advantages such as exceptional mixing effect and substantial interfacial area between the phases. However, there is a lack of attention to the mechanism of CO2 absorption by individually-tracked moving solid sorbents as well as their effects on the decarbonization performance in a gas–solid fluidized bed. In this study, CO2 removal model by solid particles based on MgO adsorbent was established with the implementation of the shrinking-core model and each particle was tracked individually. Results validated the accuracy of the absorption model and revealed that smaller sizes of the solid absorbent, lower inlet gas velocities and larger inlet CO2 mass fractions exhibit relatively high CO2 removal efficiency. In addition, the decarbonization performance of fluidized and packed beds was compared. The packed bed exhibits more uniform gas flow and higher CO2 removal efficiency, whereas the fluidized bed provides larger interphase contact area, which facilitates the heat transfer process. Through the analysis of a series of parameters, the results provide recommendations for improving the CO2 removal efficiency and help to explore the optimal protocol for the design of bed reactors for CO2 removal.