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The role of the gas±liquid separator on hydrodynamic characteristics in an internal-loop airlift reactor (ALR) was investigated. Both gas holdup and liquid velocity were measured in a 30 dm 3 airlift reactor with two different head con®gurations: with and without an enlarged separator. A magnetic tracer method using a neutrally buoyant magnetic particle as¯owfollower was used to measure the liquid velocity in all sections of the internal-loop airlift reactor. Average liquid circulation velocities in the main parts of the ALR were compared for both reactor con®gurations. At low air¯ow rates the separator had no in¯uence on gas holdup, circulation velocity and intensity of turbulence in the downcomer and separator. At higher super®cial air velocities, however, the separator design had a decisive effect on the hydrodynamic parameters in the downcomer and the separator. On the other hand, the gas holdup in the riser was only slightly in¯uenced by the separator con®guration in the whole range of air¯ow. Circulation¯ow regimes, characterising the behaviour of bubbles in the downcomer, were identi®ed and the effect of the separator on these regimes was assessed. # 2001 Society of Chemical Industry Keywords: airlift reactor; separator; circulation regimes; circulation velocity;¯owfollower

No abstract