Power Consumption in Dual Impeller Gas-Liquid Contactors: Impeller Spacing, Gas Flow Rate, and Viscosity Effects

Abstract

The dependence of power consumption on impeller spacing, and also in relation to gas flow rate and viscosity, in unaerated and aerated gas-liquid contactors agitated by dual Rushton-and by dual pitched blade turbines was comparatively studied. In tap water the two Rushton impellers acted independently for spacings greater than DH = 1.65d, while in glycerol solutions the impellers acted independently on reaching an impeller spacing equal to 1.20d; the corresponding values for the two pitched blade impellers were 1.50d for tap water, 1.07d for relatively high viscosities, and 0.53d for very high viscosity values. The Newton number Ne decreases with increasing viscosity for the dual Rushton turbine systems, while an increase of Ne can be observed with increasing viscosity for the corresponding pitched blade systems. For the dual Rushton turbines, gas flow number Q has no effect on Ne, at very high values of viscosity, while at low and relatively high viscosity values a small effect of Q on Ne can be detected. As observed for the dual Rushton turbine systems, Ne is also not affected by Q for the corresponding pitched blade systems at very high viscosity values. Flow number Q does not significantly affect the Newton number for the water-glycerol solutions with a relatively high viscosity agitated by dual pitched blade turbines, while for the aerated water systems a decrease of Ne can be observed at relatively small gas flow numbers; high values of Q do not affect the Newton number.

Influence of Spacing of Multiple Impellers on Power Input in an Industrial‐Scale Aerated Stirred Tank Reactor

“…Independent behavior of impellers has been reported for pitched blade turbines in tap water as starting with a spacing of 1.55d, while for two Rushton turbines it has been reported to start at a greater spacing of 1.65d [30,31,34]. For small gas flow rates, a sharp increase in Po is reported for dual Rushton turbines for spacing in the range of 0.6 to 0.8d, which is much smaller for higher gas flow rates [34]. For a dual pitched blade configuration, the effect of impeller spacing on power consumption is reportedly smaller in the flooded regime than for a dual Rushton configuration.…”

“…For a dual pitched blade configuration, the effect of impeller spacing on power consumption is reportedly smaller in the flooded regime than for a dual Rushton configuration. However, a dual pitched blade configuration already starts acting independently at a spacing of 0.45d for high gas flow rates [34].…”

Μελέτη Των Καταστάσεων Πλημμύρισης Σε Αναδευόμενα Συστήματα Αερίου-Υγρού

“…Οι χαρακτηριστικοί αριθμοί Froude στην μετάβαση στην πλήρη διασπορά συναρτήσει εκείνων στην μετάβαση στην πλημμύριση για δύο διαμέτρους προωθητήρα, d=0.33D και d=0.49D [45].…”

“…Παράλληλα, είναι αξιοσημείωτο το γεγονός ότι στην πλημμύριση το σύστημα ανάδευσης δεν μπορεί να αξιοποιήσει την ισχύ που καταναλώνει. Αυτό προκύπτει και από το Σχήμα 7.2 που ακολουθεί, το οποίο αναφέρεται σε σύστημα με διπλούς προωθητήρες Rushton και διάμετρο d=0.52D[45]. Σύμφωνα με τη βιβλιογραφία[37,40,41,42], τα συστήματα με διπλούς προωθητήρες δεν διαφέρουν ως προς τα χαρακτηριστικά μετάβασης στις διάφορες καταστάσεις διασποράς.…”