The improvement of the heavy water enrichment under countercurrent-flow Frazier scheme and flow-rate fraction variations

The desirable cascading effect and undesirable remixing effect are the two conflicting effects produced in a thermogravitational thermal-diffusion column. A new design is proposed in the present study to obtain equilibrium separation efficiency improvement associated with a remixing-effect suppression and cascading effect enhancement. The separation equation for the heavy water enrichment by inclined thermal-diffusion columns in countercurrent-flow Frazier schemes under flow-rate fraction variations has been developed theoretically. The concentration-product term in the transport equation is treated in the enriching and stripping sections separately for more accurate analysis. It was found that the undesirable disadvantage of the remixing effect could be reduced effectively by suitably tilting the column and controlling the flow-rate fraction at both top and bottom product streams, leading to a considerable separation efficiency improvement. Numerical examples were given to illustrate the best inclination angle and flow-rate fraction on separation efficiencies for H2O-HDO-D2O system.