Study of axial mixing, holdup and slip velocity of dispersed phase in a pulsed sieve plate extraction column using radiotracer technique.
Axial mixing, holdup and slip velocity of dispersed phase which are parameters of fundamental importance in the design and operation of liquid-liquid extraction pulsed sieve plate columns have been investigated. Experiments for residence time distribution (RTD) analysis have been carried out for a range of pulsation frequency and amplitude in a liquid-liquid extraction pulsed sieve plate column with water as dispersed and kerosene as continuous phase using radiotracer technique. The column was operated in emulsion region and (99m)Tc in the form of sodium pertechnetate eluted from a (99)Mo/(99m)Tc generator was used to trace the dispersed phase. Axial dispersed plug flow model with open-open boundary condition and two points measurement method was used to simulate the hydrodynamics of dispersed phase. It has been observed that the axial mixing and holdup of dispersed phase increases with increase in pulsation frequency and amplitude until a maximum value is achieved while slip velocity decreases with increase in pulsation frequency and amplitude until it approaches a minimum value. Short lived and low energy radiotracer (99m)Tc in the form of sodium pertechnetate was found to be a good water tracer to study the hydrodynamics of a liquid-liquid extraction pulsed sieve plate column operating with two immiscible liquids, water and kerosene. Axial dispersed plug flow model with open-open boundary condition was found to be a suitable model to describe the hydrodynamics of dispersed phase in the pulsed sieve plate extraction column.
Flooding and axial dispersion in reciprocating plate extraction columns
The flooding and axial mixing characteristics of a 15 cm diameter reciprocating plate extraction column with six different plate arrangements handling kerosene dispersed in water are reported. A general correlation for flooding in the emulsion flow regime is developed and applied to the present results and to published data on other columns and systems. Under certain conditions of flow and agitation, the axial mixing is very high because of circulation, but it can be reduced by including baffles in the plate stack. 
 
 
 
On presente les caracteristiques relatives a l'engorgement et au melange axial d'une colonne d'extraction de 15 centimetres de diametre avec plateaux alternatifs; il y avait six arrangements differents des plateaux et Ton a utilise du kerosene disperse dans l'eau. On a mis au point une correlation generate pour l'engorgement dans le regime d'ecoulement sous forme d'emulsion et on l'a appliquee aux resultats du present travail ainsi qu'a ceux qui ont deja ete publies relativement a d'autres colonnes et systemes. Dans certaines conditions de debit et d'agitation, le melange axial est tres eleve par suite de la circulation, mais on peut le diminuer en introduisant des chicanes dans l'empilement des plateaux.
Drop size and holdup in a reciprocating plate extraction column
This paper reports measurements of droplet sizes and holdup in liquid—liquid systems in a 2 in. dia. reciprocating plate extraction column, in the absence of mass transfer. 
 
The Sauter mean droplet diameter was found to depend on the product of plate amplitude and frequency and on the system properties, but it was not in general affected by the throughput. It could be correlated fairly well using a turbulent dispersion model similar to that which has been applied successfully to dispersions in stirred tanks. 
 
A simple hydrodynamic model is proposed for the holdup, assuming the droplet diameter to depend on turbulent energy dissipation. This model is consistent with the experimental data if it is assumed that droplets in kerosene undergo hindered circulation while droplets in methyl isobutyl ketone circulate freely. The model also agrees with some previously published data on holdup in a gas—liquid system in a pulsed column, assuming that the gas bubbles circulate freely.