Hydrodynamics Study Of Gas-liquid-solid Fluidized Bed

As aerobic biological fluidized beds play a more and more impotant role in city wastewater treatment, the study of hydrodynamics was meaningful.Experiments were conducted in a gas-liquid-solid fluidized bed with waste coke particles as solid, air and tapped water as the gas and liquid. The column is 1.7 m in height and 100 mm in diameter, coke particle size is 1.07 mm. CFD simulation and experiments were carried out to learn the the radial distribution of local holdups. The simulation is compared with experimental data. The significance of available turbulence model,bubble diameter were investigated. When the bubble diameter,the RNG model was able to better caputre depiction of flow pattern than standard and laminar model. The 3D model shows a better predictiton of the flow characteristics than the 2D mode. The choice of bubble diameter was influlential and should be carefully treated. The distribition of local Gas holdups were uniform close to the wall, while far from the distribiton board, local gas holdups decreased along the radial. Local solid holdups increased in the wall at the location near the entrance. While at the location away from the entrance, solid holdups decreased in the wall.Electrical conductivity probe and reflective optical probe were employed to measure local gas holdups and local solid holdups along the radial. Results showed that for the fluidized system, under different superficial gas velocities from 0.35 to 0.71 cm/s and superficial liquid velocities from 2.12 to 3.54 cm/s, the distribution of local gas holdups was uniform in the center region,and decline in the wall. The gas holdup increased while the superficial gas velocity increased, and descended while the superficial liquid velocity increased. The distribution of local gas holdups at different axial location(H=370, 470 mm) was consistent, and increased with the increase of height. The distribution of local solid holdups was uniform along the radial, and decreased with the increase of height. At different axial location(H=370, 470 mm) the distribution of local solid holdups was consistent.