Axial dispersion in the gas, liquid, and solid phases

To this author s knowledge, no data on three-phase stirred columns are available. Preliminary observations indicate that the axial dispersion in the gas phase is considerably reduced by the presence of solid particles. Under certain conditions, even for a very low L/dc (where L is the length and dc the diameter of the stirred column) the gas phase may move essentially in plug flow. 

A review of the gas-phase axial dispersion in a stirred and unstirred bubble-column in the absence of solid particles is given by Ostergaard.97 

A review on earlier studies of liquid-phase axial dispersion in unstirred bubble-columns with no solids is given by Ostergaard.97 Van de Vusse138 has discussed the liquid-phase RTD in stirred slurry reactors. 

The effects of suspended solid particles on liquid-phase axial dispersion in a cocurrent-upflow system have been studied by Schiigerl123 and Michelsen and Ostergaard.82 They showed that, in a three-phase column, the axial dispersion increases with gas rate. Unlike in a gas-liquid bubble-column, the liquid-phase axial dispersion coefficient in a three-phase column depends upon the liquid velocity. The nature of the effect is, however, dependent upon the gas rate and solids particle size. Similarly, the nature of the effect of solid size on the axial dispersion depends on the gas and liquid flow rates. 

Kim et al.56 correlated their data for liquid-phase backmixing in a three-phase rectangular column by a dimensionless correlation  

---