Abstract:

A stimulus-response technique was used to determine the residence time distribution (RTD) of liquid phase in the gas-liquid-solid mini-fluidized bed with 3 mm bed diameter. Deionized water and air were used as liquid phase and gas phase, respectively. Glass beads and alumina particles with the mean particle size of 0.123-0.222 mm were taken as solid phase. KCl tracer as an input signal was injected into the fluidized bed through a sample injector. The RTD of liquid phase was obtained by analyzing the conductivity at the bed outlet. The results indicate that the RTD become significantly smaller with the increase of superficial liquid and gas velocities. The mean residence time increases at lower superficial liquid and gas velocity or with the addition of solid particles. The flow is close to laminar flow when the superficial liquid velocity is set at 1.96-15.70 mm×s^-1, meanwhile superficial gas velocity 1.18-1.96 mm×s^-1. The mean residence time of liquid phase in the gas-liquid-solid mini-fluidized bed is (19.6±0.34) s-(48.0±0.92) s. A correlation of the Peclet number is able to predict the experimental data within a relative deviation of ±25%. The research results have guiding significance for the design amplification of small three-phase fluidized bed.

Key words: fluidized-bed, gas-liquid-solid mini-fluidized bed, residence time distribution, laminar flow, multiphase flow

摘要：

采用脉冲示踪技术，研究了3 mm床径的小型气-液-固流化床内液相停留时间分布。以KCl为示踪剂，液相为去离子水，气相为空气，固相为平均粒径0.123~0.222 mm的玻璃微珠和氧化铝颗粒，测量流化床出口液相的电导率，得到其停留时间分布曲线。结果表明，增大表观液速和表观气速，分布曲线变窄，平均停留时间缩短，Peclet数增大；固相的存在使液相的平均停留时间增长。表观液速1.96~15.70 mm×s^-1，表观气速1.18~1.96 mm×s^-1的条件下，流动接近层流；平均停留时间的范围为（19.6±0.34）s~（48.0±0.92）s，建立的Pe经验关联式对实验结果有较好的预测，偏差在±25%以内。研究结果对于小型三相流化床的设计放大具有指导意义。

关键词: 流化床, 小型气-液-固流化床, 停留时间分布, 层流, 多相流