Drop size and hold-up in countercurrent extraction with supercritical CO2 in a spray column

The drop size and hold-up were measured in a continuous countercurrent extraction spray column of 22.7 mm i.d. under near-critical and supercritical conditions. The drop size was measured by analysis of images and hold-up by the shut-off method. The systems studied were 5 and 10 vol % 2-propanol + water and 10 vol % ethanol + water extracted with carbon dioxide, at temperatures from 25 to 45 degreesC and pressures from 6.9 to 13.8 MPa. Data were correlated with physical properties of the system. The model developed to predict the drop size agreed favorably with experimental data with an average absolute relative deviation (AARD) of 5.6%. In the case of hold-up, the AARD was 12.4%.