装配水平筛板的气升式反应器中气液传质特性的数值模拟

利用Turbulent–Lehr组合模型对装配水平筛板的气升式反应器进行了计算流体力学(CFD)模拟，研究水平筛板对气含率、气泡直径、体积传质系数(kLa)和气液流速的影响。结果表明，筛板对气相的囤积作用和对液相的阻碍作用增加了反应器的整体气含率。筛板对气相的二次均布作用减弱了筛板和液面之间区域的气泡聚并过程，筛板筛孔对气泡的破碎作用产生了大量小于初始直径的气泡，增加了气泡比表面积(a)；筛板对液相的阻碍作用提高了筛板附近的气–液相流动速度差，从而提高了该区域的液膜传质系数(kL)，强化了反应器内的气液传质效果。

Numerical simulation of mass transfer characteristics in an airlift reactor with a horizontal sieve plate

A CFD simulation of the mass transfer and flow field characteristics of gas–liquid two phases in an airlift reactor with a horizontal sieve plate was carried out by combining turbulent aggregation kernel with Lehr breakage kernel in the population balance model. The simulation results agreed well with the experimental results. The effects of horizontal sieve plate on the gas holdup, bubble diameter, volumetric mass transfer coefficient and gas–liquid flow field and velocity in the airlift reactor were investigated. It showed that the accumulation of the gas phase beneath the sieve plate increased the local gas holdup in the region, thereby increasing the overall gas holdup in the reactor. The forced re-distribution on the gas phase by the sieve plate attenuated bubble coalescence in the region between the sieve plate and the liquid surface, thereafter, decreased bubble diameter and increased the specific surface area of bubbles. A large number of bubbles smaller than the bubbles with the initial diameter were generated by the holes on the sieve plate with the breakup action, which increased the specific surface area of bubbles near the sieve plate. The velocity difference between the gas and liquid phases in the vicinity of the sieve plate was increased by the retardation on the liquid phase, thus improving the mass transfer coefficient of the liquid film in the region. The sieve plate reduced the flow velocities of liquid and gas in the reactor, thereby increased the contact time between the gas and liquid phases, increased the overall gas holdup of the reactor and enhanced the gas–liquid mass transfer. The volumetric mass transfer coefficient in the reactor was improved by assembling the horizontal sieve plate. The works would be beneficial to optimized internal structure of the airlift reactor and its applications.