A simple multistage internal airlift loop reactor (MIALR)

which has been widely employed in the chemical industry

was designed and investigated. The influences of interstage height and superficial gas velocity in the MIALR on the performance of the mixing and mass transfer were inspected. Three typical regimes

i.e.

abnornal

transition and regular regimes

in the MIALR were observed and proposed in this work for the first time. There were two critical superficial gas velocities impacted by the interstage height in the MIALR for the flow regime transition

and two mathematical models were proposed here for the prediction of flow regimes. The results showed that a higher superficial gas velocity was desired for reaching a regular regime when the interstage height of the MIALR increased. In addition

the respective gas holdups in the riser and the downcomer would be promoted if there was an increment of the interstage height in the MIALR. The gas holdups in the riser and the downcomer at the third stage were the highest at the same conditions

and those at the first stage were the lowest among the three stages in the reactor. Moreover

the higher the interstage height

the higher the circulating liquid velocity in the downcomer was. The highest circulating velocity in the downcomer was measured at the first stage

and the lowest value was obtained at the third stage. Finally

a reduction of mixing time was gained when the interstage height increased

while an increase of volumetric mass transfer coefficient was obtained at the same conditions. Therefore

a guideline for the scientific design

scaling up and operating of this kind of industrial MIALRs was provided.