A new calcification-carbonation method was developed for treating bauxite residue (red mud), and a novel Venturi carbonation reactor (jet-flow reactor) was designed and used to process the bauxite residue. The characteristics of the fluid of gas-liquid and red mud slurry-gas-liquid phases in the jet flow reactor were investigated, mainly the effects of superficial gas and liquid velocities and the effective height-to-diameter ratio (H/D) of the reactor for gas holdup, mixing time, bubble refining, and CO2 absorption. The results show that the maximum CO2 utilization rate (eta) was achieved, i.e.eta = 833% when the H/D value of the reactor was 4 and superficial gas and liquid velocities were 10.62 m.s(-1) and 0.89 m.s(-1), respectively. The results provide a theoretical basis for the optimization of a new type of jet flow reactor. (C) 2017 Elsevier B.V. All rights reserved.