MIXING STUDIES IN EXTERNAL-LOOP AIRLIFT REACTORS

The mixing behaviour of the liquid phase in two external-loop airlift reactors of laboratory and pilot scale, in terms of the mixing time an d axial dispersion, was investigated. The mixing parameters were deter mined from the output curves to an initial Dirac pulse, using the clas sical tracer response technique, and analysed in relation to operating and geometrical parameters, such as v(sGR),A(D)/A(R),H-d and D-R. Mix ing in the external-loop airlift reactors under investigation was esse ntially correlated with the liquid circulation velocity. The specific sections of the airlift reactor have different mixing behaviour, so th at the riser and downcomer can be analysed as plug flow with axial dis persion, whereas the top section approaches ideal mixing behaviour. A simple correlation between the specific mixing time and the operating and geometrical parameters was developed which can be used for design and scale-up purposes. (C) 1997 Elsevier Science S.A.