INVESTIGATION OF FEEDPIPE BACKMIXING IN AN AGITATED VESSEL

Feedpipe backmixing in an agitated vessel was investigated using a new ly developed conductivity technique. By this technique, the onset of f eedpipe backmixing could be detected and the penetration depth of the vessel fluid into a feedpipe was determined. For a given feedpipe flow rate, critical agitator speeds to eliminate feedpipe backmixing were d etermined using Rushton six-bladed disk turbine impeller (6BD) and hig h efficiency, axial-flow type 3-bladed impeller (HE-3) of 8.89 and 12. 70 cm diameters in 11.2 liter reactor. The ratio of the feedpipe veloc ity to the critical agitator speed (v(f)/v(t)) was determined as a fun ction of feedpipe Reynolds number (N-Ret). The conductivity technique was successful either in the laminar regime, the transitional regime, or in the turbulent regime in the feedpipe.