Effect of a diffuser on gas-solid behavior in CFB riser for CO2 capture

Gas-solid fluidized beds have been used in CO₂ capture processes because of their high mixing characteristic and heat and mass transfer. Sufficient residence time of solid particles in a reactor is required to capture CO₂. However, a fraction of solid particles pass through a reactor without capturing CO₂ due to normal reaction characteristics. Therefore, the objective of the present study was to increase the sorbent residence time using a diffuser in a reactor for CO₂ capture. An Eulerian-Eulerian model in a commercial CFD program was employed to simulate gas-solid flow in the reactor. First, sensitivity analysis depending on operating conditions was conducted to predict the residence time of solid particles. The diffuser was located in the middle of the reactor and the angle of the diffuser was changed. Solid particles dispersed in the radial direction because of gas characteristics in the diffuser and increased the residence time. The results showed that the diffuser increased the sorbent residence time, so that the probabilities of gas-solid reaction would be also improved.