鼓泡床中电石渣液相碳酸化反应流动特性表征

搭建了气液固鼓泡床实验系统,对碱性固体废弃物电石渣固定CO₂进行实验研究. 流动特性对鼓泡床反应器传质、产率和产品质量都有较大的影响. 通过压力脉动信号采集与分析,对实际反应体系CO₂-H₂O-电石渣的流动特性进行表征,给出重要参数液固比对三相反应流流动特性的影响机制. 结果表明:基于时间域的概率密度函数和自相关函数分析发现,在低气速0.062 m·s^-1下,增大液固比,压力脉动分布变化较小,但自相关分析可进一步揭示液固比的增大加大了气泡运动的不稳定性. 在气速0.102 m·s^-1下,液固比增大会加大压力脉动分布范围,且延迟时间增大,自相关性降低,表征床内流动表现出更多的随机性和混沌特征. 结合流动图像,液固比增大使大气泡容易聚并生成. 基于时频域的Hilbert-Huang变换分析,获得了时间-频率-幅度谱图. 低气速下,三相流运动频率高,幅值低,增大液固比后,三相流运动频率降低,幅值增大,揭示液固比增大后,三相流系统中高频的小气泡运动特性降低,大气泡聚并发生促进能量幅值增大,该结果为进一步研究流动对碳酸化反应影响机理奠定了基础.

Characteristics of Carbide Slag Slurry Flow in a Bubble Column Reactor

A gas-liquid-solid bubble column experimental system is set up and the direct aqueous carbonation of the carbide slag is experimentally evaluated and studied. Hydrodynamics of the bubble column has a great effect on the bed mass transfer and product yield and quality. The flow behaviors for a real reaction system of CO₂-H₂O-carbide slag are characterized through the bed pressure signal analyzation. The effect of the important parameter liquid to solid(L/S)ratio on the flow dynamics of the three-phase reacting flow is revealed. The time domain and the time-frequency domain analysis of the signals are carried out. The results show that the curves of the probability density function have the similar distributions when increasing the L/S ratio at 0.062 m·s^-1. The results of the auto-correlation function analysis reveal that the bed bubble flow is unsteady and irregular at 0.062 m·s^-1 when increasing the L/S ratio. The change amplitudes of the pressure signals become wider at 0.102 m·s^-1 with an increase in the L/S ratio. The delay time increases in this condition which indicates that the pressure signals are not similar and the three-phase flow is more random and stochastic. The large bubbles are easier to form when observing the flow images. The time-frequency-amplitude spectrums are obtained and it is found that the three-phase flow has the lower frequency and the higher energy amplitude with an increase in the L/S ratio,which contributes by the bubble coalescence. This work gives a theoretical basis for the further study on the effect of the flow dynamics on the carbonation reactions.