电导探针法测量高固含体系循环液速和气含率

Measurement of Liquid Circulation Velocity and Gas Holdup in a System at High Solid Concentration with an Electric Conductivity Probe

基于电导探针和示踪法,开发了一种利用电导探针同时测量环流反应器中高固含体系下循环液速和局部气含率的方法.利用2个单针电导探头测量脉冲注入KCl饱和溶液后两路电导信号的先后响应,测得两路液体的停留时间分布曲线.通过对单路信号进行幅值分析可以得到气含率,与压差法相比测量值误差小于5%;通过对过滤气泡信号后的液体的停留时间分布曲线进行相关处理可得到循环液速,测量值与超声多普勒(UDV)的测量结果一致.实验研究了外环流反应器中操作条件对气含率和循环液速的影响.结果表明,低表观气速下气含率沿径向分布较均匀,高于0.1m/s后逐渐呈抛物线型分布,整体随表观气速增加而增大;循环液速随表观气速增加近似线性增大,随固含率增加而减小.

A measurement method of liquid circulation velocity and local gas holdup at high solid concentration in an airlift reactor simultaneously was developed, based on two probes of electrical conductivity tip and tracing method. Two residence time distribution （RTD） curves were obtained by measuring the concentration changes of tracer （saturated solution of KC1） injected into the riser by using two probes. The gas holdup was obtained by analyzing one RTD curve, with an average discrepancy within 5%. The liquid circulation velocity was determined by correlation of the two RTD curves after filtering bubble signals, and the results were consistent with the values measured by ultrasound Doppler velocimetry. The effects of operating conditions on gas holdup and liquid circulation velocity were investigated in an external-loop airlift reactor. The results show that the gas holdup increases with increasing superficial gas velocity, and the radial distribution of gas holdup is uniform with the superficial gas velocity less than 0.1 m/s, however, parabolic distribution with the superficial gas velocity larger than 0.1m/s. The liquid circulation velocity increases almost linearly with increasing superficial gas velocity, and decreases with increasing solid holdup.