The axial dispersion coefficients in the continuous phase and holdup of dispersed phase have been studied in a 4.2 cm inside diameter and 200 cm height pulsed doughnut-disc type plates extraction column.
The axial concentration gradient in a continuous extraction column was expressed mathematically in terms of Peclet number by axial dispersion model. Peclet numbers have been calculated from response curves using KCI solution as an impulse input tracer.
Experimental data have been taken for both continuous and dispersed phase with plate spacing, pulsing amplitudes, frequencies, and superficial velocities as system variables. Modified axial dispersion coefficients have been correlated by regression analysis of experimental data, and following equations were obtained.

1. Axial dispersion coefficient （single phase）
E_C = 3.5H^-1.3 A^1.54f + 30.95 U_C
2. Axial dispsion coefficient (two phase)
E_C = 2.36 H^-0.8 A^1.34 f + 20.89 U_C
3. Fractional holdup of the dispersed phase
_d = 4.2×10^-5 H^-0.44 A f^1.28 U_d^0.93