Hydrodynamics and heat transfer coefficients during CO₂ carbonation reaction in a circulated fluidized bed reactor using 200 kg potassium-based dry sorbent

Dry sorbent CO₂ capture process is a proven technology to remove CO₂ efficiently from flue gas. The current system was used to understand the effect of solid inlet height (H_in) and horizontal heat transfer tubes on solid hydrodynamics in the fast fluidized bed (FFB). Also, the ranges of stable hydrodynamic conditions were visually confirmed at the varied H_in, gas velocity (U_g) and solid circulation rate (G_s). The changes in the suspension density (ρ_sus) during CO₂ carbonation reaction was experimentally measured and matched to the ρ_sus at the specific gas velocity under no reaction bed. It showed that the ρ_sus at the initial U_g = 1.4 m/s under the reaction mode increased to that at 1.04 m/s along the bed due to the carbonation reaction. Heat transfer coefficients (HTC) were obtained during CO₂ carbonation operation over 80 h, which resulted in CO₂ removal efficiency (85%) and CO₂ purity (96%). Finally, the effect of ρ_sus was determined to be the most significant factor on HTCs, ranged from 135 to 215 W/m²∙^oC during the carbonation reaction. It indicated that the different local HTCs at different bed heights were observed at the carbonation or no reaction modes due to the exothermic reaction heat.