Bubble dispersion greatly relies on spargers. Single or ifice and porous spargers were tested inside a bubble column under a low gas thr oughput to study their influences on gas dispersion and gas-liquid interface ar ea. A PBE model without considering the effect of bubble coalescence was develo ped to describe axial bubble distribution. Both simulation and experimental res ults showed that bubbles broke up much faster than coalesced under low gas veloc ity. For a single orifice sparger, breakage was a dominant feature for bubbles after they left the orifice. Initial bubbles formed over the orifice were mostl y 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 l argest stable bubble. The bubbles possessed smaller size and narrower distribut ion compared with the bubbles obtained by single orifice spargers. With the por ous sparger, gas-liquid surface area was increased by 5—6 times even though th e gas holdup changed insignificantly. High mass transfer area could be obtained by injecting more small initial bubbles with diameters under d_s.
