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 ds 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 ds.