单孔及微孔曝气低气速鼓泡床内气泡行为比较

引言鼓泡床反应器被广泛应用于吸收、液相氧化、好氧生化等气液反应过程,气体在液相中的分散情况对鼓泡床的反应和传质特性都有很大影响.为了提高气液传质效率,增加生产强度,工业反应器很多都是在高气速下操作(Ug>0·05m·s-1),很多研究都集中在高气速湍动鼓泡区1~3].但对有机

Comparison of bubble behavior between single orifice and porous spargers air-water bubble columns

Bubble dispersion greatly relies on spargers. Single orifice and porous spargers were tested inside a bubble column under a low gas throughput to study their influences on gas dispersion and gas-liquid interface area. A PBE model without considering the effect of bubble coalescence was developed to describe axial bubble distribution. Both simulation and experimental results showed that bubbles broke up much faster than coalesced under low gas velocity. For a single orifice sparger, breakage was a dominant feature for bubbles after they left the orifice. Initial bubbles formed over the orifice were mostly larger than the largest stable bubble. They broke up quickly and their sizes were reduced below the maximum diameter d_s of stable bubbles. In contrast, a porous sparger produced a large amount of initial bubbles smaller than the largest stable bubble. The bubbles possessed smaller size and narrower distribution compared with the bubbles obtained by single orifice spargers. With the porous sparger, gas-liquid surface area was increased by 5—6 times even though the gas holdup changed insignificantly. High mass transfer area could be obtained by injecting more small initial bubbles with diameters under d_s.