CONCENTRIC-TUBE AIRLIFT REACTORS - EFFECTS OF GEOMETRICAL DESIGN ON PERFORMANCE

Pressure drops, gas holdup, and mass-transfer coefficients were measur ed in two concentric-tube airlift reactors of 30 and 300 L (nominal vo lume). The aspect ratio and the ratio of riser to downcomer cross sect ion were the same for both reactors, but the geometry of the gas separ ation section was different. The influence of the bottom and top clear ances was studied using water and carboxymethyl cellulose solutions an d covering a range of effective viscosity from 10(-3) to 25 x 10(-3) P a.s. The pressure drop results expressed as a Euler number were satisf actorily correlated with Fr, Ga, and a bubble disengagement group M. C orrelations are presented also for the gas holdup in the riser, downco mer, and gas separator. The last-mentioned coincides with the correlat ion for the total holdup in the reactor. The gas-liquid mass-transfer coefficients for all the liquids and geometric variables in both react ors were successfully correlated as Sherwood numbers.