射流鼓泡反应器的混合特性

摘要

射流鼓泡反应器以液体射流代替搅拌实现液相混合，具有结构简单、制造及维护费用低等诸多优点，研究其混合特性对于反应器的设计、优化及放大具有重要意义。以空气-水作为模拟介质，采用KCl电解质溶液为示踪剂考察了表观气速和射流Reynolds数的大小对液相宏观混合时间的影响，并从能量输入的角度对射流鼓泡反应器的混合机制进行分析。研究发现，在实验条件下（表观气速变化范围为0.0006～0.0343 m·s−1，射流Reynolds数的变化范围为1.75×104～7.00×104），鼓泡的加入使得均相射流反应器内的液相混合得到改善；随着表观气速增大，液相宏观混合时间先缩短后延长；当气体输入功率或液体输入功率不变时，混合时间随总输入功率的增大而缩短。通过对多组实验数据的回归分析，提出了液相宏观混合时间与液体输入功率和气体输入功率的经验关联式，计算值与实际值吻合较好。最后基于提出的关联式，发现当总输入功率一定时，混合时间随气体输入功率的增加先缩短后延长，临界转变点在气体输入功率为总功率的61%处，此时气液两相协同作用最强。%The jet bubbling reactor uses liquid jet to achieve the liquid mixing instead of mechanical stirring, which brings several advantages such as simple structure and low cost of maintenance and manufacturing. The research of its mixing characteristics plays a significant role in the design, optimization and scaling up of the reactor. Based on the air-water system, the electrolyte tracer (KCl solution) method was applied to investigate the influences of gas velocity and jet Reynolds number on the liquid mixing time with the cold model experimental apparatus. The mixing mechanism in jet bubbling reactor had also been analyzed from the perspective of power input. The results showed that within the experimental range (ugfrom 0.0006 to 0.0343 m·s−1,Rej from 1.75×104 to 7.00×104), the introduction of gas bubbling strengthened the liquid mixing conditions. With the increase of superficial gas velocity, the liquid mixing time decreased at first and then increased. When the gas or liquid power input kept constant, the mixing time decreased with the increase of the total power input. Through the regression analysis of all the experimental data, relationship between liquid mixing time, and liquid and gas power inputs had been built up. An empirical correlation was proposed, and the calculated value was fitted well with the experimental data. Based on the obtained equation, the liquid mixing time was found to decrease at first and then increase with the increase of the gas power input if the total power input was remained constant. The transition point was around where gas input power occupied 61% of the total input power. At this point, the synergistic effect was the strongest.