Diffusional effects of packed beds for multistage separation

The multistage separation system using adsorption and desorption is difficult to enlarge because the imaginary equivalent height (Hq) is less than a few millimeters. Several experiments with uranium enrichment as a typical multistage separation process showed that separation efficiency was in the range of 3.2 to 4.4 %, even when the contributions of adsorbent and chemical reactions to Hq were taken into account. The diffusional effects of packed beds were evaluated by the pulse response method and were represented by an imaginary equivalent height in the mobile phase (Hm). A modified Gaussian distribution was used for this analysis. It was found that the scattering of separation efficiency is caused by the diffusional effects of packed beds. The values of Hm are in the range of 0.4 to 0.6 mm, or about 30 to 40 % of Hq. (author)