Optimum Feed Point for Isotope Separating Thermal Diffusion Column

Abstract

A relation satisfied by an optimum feed point (axial height l _opt: a dimensionless height from the bottom), which maximize separation factor (and, then, separative power), was derived based on an approximate column constants in terms of operating condition such as temperature difference between hot and cold walls ΔT, feed flow rate F, pressure P, and cut ϑ as well as geometrical condition of thermal diffusion column for isotope separation. The value of l _opt is obtained through Newton iterative solution of this relation. As for an ordinary cold-wall (T _c=288 K) thermal diffusion column separating H₂-HT (Tracer level: 7.3x10⁻¹⁰) mixture, the authors got l _opt= −0.2 for operating conditions that ΔT=1,000K, F=5 x 10⁻⁵m³ (i.e. 50 cm³)/min (at 0.1 MPa, 288K), and ϑ=0.5. The optimum point obtained through a rigorous two-dimensional analysis by changing parametrically the feed point was l _opt=–0.17, and the optimum point can, therefore, be predicted well even by the present simple model. Moreover, the optimum feed position exists closely near the point where the radially averaged HT-concentration coincides with the feed mole fraction.

KEYWORDS:

• thermal diffusion column
• isotope separation
• feed point
• Newton iterative procedure
• separative power
• separation factor
• cut
• feed flow rate
• temperature difference
• temperature dependence