SINGLE-PHASE AXIAL MIXING STUDIES IN PULSED SIEVE-PLATE LIQUID-LIQUID-EXTRACTION COLUMNS

Axial mixing phenomena in pulsed sieve plate liquid-liquid extraction columns have been studied using the stationary phase tracer technique. Based on 270 data points and covering a wide range of column geometry , the following correlation was obtained: E(0) = a(rho(c)d(0)fA/mu(c)) (-0.3)(fA)(1 )C(D)(2))(0.33)+b(fA(2)/e(2))(h/a)(0.45),m(2)s(-1) The ab ove two-term correlation was found to be necessary in order to disting uish axial mixing effects close to the plates and those in the main bo dy of the column compartments, the latter effect becoming dominant as plate spacing increases. The preconstant 'a' was found to be approxima tely in inverse proportion to the column diameter D, possibly due to w all effects, whereas the preconstant 'b' was approximately constant. T he axial mixing was found to be at a minimum for plate spacings in the range of 45 to 80 mm and the large increases in axial mixing for plat e spacings outside this range help to explain the lack of agreement in the correlations of previous workers. The form of the correlation (wi th proper dimensions) suggests that the functional dependence of axial mixing coefficient on amplitude and frequency of pulsation varies fro m fA to fA(1.5), according to the relative magnitudes of the two terms . The effect of column diameter, for column diameters from 40 to 152 m m examined in this work, is found to vary from about D-0.3 to D-1. The effects of plate voidage e, plate spacing h and plate hole size d(0) are now well-represented over wide ranges, as well as the effects of v iscosity. The stationary phase tracer technique employed in this study provided a very convenient and adequate means of study and led to res ults that are in good agreement with those of other single phase measu rement techniques.