Numerical Simulation On Carbonation Reactor Of Calcified Residue

According to the problems about the low utilization of low-grade bauxite in industry and high-alkali and high-aluminum content in Red Mud, our group proposed a new method called "Calcification-Carbonation" to process low-grade bauxite and red mud. This paper aimed at studying the carbonation process-the core process of "Calcification-Carbonation", and a venturi carbonation reactor to process calcified residue innovatively designed and produced. The simulation calculation for dynamic characteristics of gas-liquid two-phase flow and gas-liquid-solid three-phase flow were discussed in the reactor. By changing operating parameters such as the superficial gas velocity, superficial liquid velocity, liquid-solid ratio and structural parameters such as height-diameter ratio, numerical simulation of pressure field, velocity field, gas holdup distribution and solid holdup distribution were carried out in the carbonation reactor, and the simulation results were analyzed. Simulation values were compared with the measured values of the average gas holdup to verify the reliability of the model. The following conclusions were obtained.Firstly, Euler model could perform correct simulation and make exact prediction for the flow field in the carbonation reactor. Part of flowing movement in the reactor belonged to internal recirculation flow. By comparison, the steady-state simulation calculation was determined, and selected120,000as the final computational grid nodes.Secondly, gas velocity, liquid velocity and solid speed in the reactor increased with the increase of superficial gas velocity. Under the same conditions, gas velocity was faster than liquid velocity which had slight differences from solid velocity. The solid holdup decreased slightly with the increase of admission velocity. The gas holdup increased monotonically with the increase of a admission velocity.Thirdly, negative pressure at the throat of venturi jet reactor increased with the increasing superficial liquid velocity. The higher negative pressure the jet reactor had, the better suction effect it got. The solid holdup had little change with the increase of admission velocity. However, when the superficial liquid velocity reached5.47m·s-1, the solid holdup decreased slightly. In the gas-liquid two-phase flow, local gas holdup in the reactor had little change-just decreased slightly. In the gas-liquid-solid three-phase flow, local gas holdup in the reactor had little change, but gas holdup at the throat of venturi jet reactor showed a downward trend.Fourthly, in the gas-liquid two-phase flow, the larger the height-diameter ratio was, the higher the gas holdup was. However, considering effective volume and Internal Circulating Fluidized Bed Reactor, the height-diameter ratio of the reactor should be reasonable.Fifthly, liquid-solid ratios had a little effect on the static pressure. As liquid-solid ratio decreased, solid mass fraction increased, and solid holdup increased. As liquid-solid ratio decreased, solid mass fraction increased and bubble coalescence intensified. Therefore, gas holdup decreased.Sixthly, simulation calculation values and measured values were in a good agreement. It showed the use of the model to discuss the simulation calculation for gas-liquid two-phase flow and gas-liquid-solid three-phase flow in the reactor was entirely feasible. It also showed the reliability of numerical simulation results.The above results had a certain reference value for the design and application of venturi carbonation reactor and provided a theoretical basis for the design of the reactor under a high temperature and a high pressure.