| Abstract: | A Karr reciprocating plate column was used in extracting caffeine from the methylation mother solution of a caffeine synthesis plant with chloroform as the extractant. Pilot tests were carried out in a 38 mm diameter column to determine holdup, flooding and mass transfer at various reciprocation velocities. Results show that the holdup in the presence of mass transfer is higher than that in the absence of mass transfer, and the height of the equivalent theoretical stage (HETS) was 0.57 m for a 99.9 % recovery at the optimum reciprocation velocity. The Karr empirical correlation for scale‐up was used to predict the column height in the design of the industrial process. A 0.4 m and a 0.6 m diameter column were used to treat 2.5 m3/h and 6.0 m3/h methylation mother solution, and the corresponding HETSs were 1.42 m and 1.53 m for a 99.9 % recovery, respectively. The axial dispersion coefficients of the dispersed phase were estimated for the 0.4 m and the 0.6 m diameter columns. For a better recovery the ratio of the axial dispersion coefficient of the dispersed phase to that of the continuous phase was about 2.7–3.0. |
