气-液-固三相磁场流态化床气泡特性及液相返混

CHARACTERISTICS OF BUBBLES AND LIQUID MIXING IN THREE-PHASE MAGNETIC FLUIDIZED BED

在含磁性固定化细胞载体-海藻酸钙凝胶粒子的气-液-固三相磁场流化床生物反应器内,实验观察、测定了低气液速下反应器的气泡特性、相含率及液相返混。得到了磁场强度、气速、液速对局部气含率、气泡速度、直径分布概率影响的关联式。提出了合理的磁场分布板形式及经修正的液相混合模型。

A new type of three-phase fluidized bed has been developed by use of a magnetic distributor plate (MDP).The bubble-supported solids operation characteristics of fluidization with the liquid velocity below the minimum fluidization velocity was investigated.The characteristics of bubbles,the distribu- tion of local holdups and liquid mixing in the MDP three-phase fluidized bed with magnetic alginate beads as the solid phase were measured by the conductive probe and the optical fiber probe.Because the distribution of magnetic field is not even,the three fluidized regions,magnetic aggregative state, chain fluidization and particulate fluidization,were investigated in the bed.The radial distribution of local holdups conform with the parabolical curve.The distribution of local gas holdups was well de- scribed by the formula. ε_(9)=(1.878-0.00368H)ε_(9)(1-Φ-)~2 Under the condition of lower gas and liquid velocity,the liquid mixing was well described by the relationship of the mixing coefficient and the modified mixing model. F(t)=1-exp,[(-t/(t(0.2852+0.0000419H^(?))Q_9^(?)] It was found that the magnetic field made particles penetrating into the bubbles and break them, and both bubble diameter and bubble velocity decreased with increase of magnetic strength.The rela- tionships of the probability of small bubbles(<2mm)and lower velocity bubbles were obtained based on the experimental results.