Preliminary design assessment of heavy water purification columns through shortcut calculations including hydraulic and mass transfer characteristics

Abstract

Heavy water having deuterium content of 99.9% and more is used as the moderator and the coolant in pressurized heavy water nuclear reactors (PHWRs). This purity is maintained by vacuum distillation in packed columns. This work analyses the effect of packing type on preliminary column design based on certain user-defined specifications, with a focus on mass transfer and hydraulic characteristics of the column. Geometrical characteristics of commercial metallic packing materials used in fractionation and gas absorption service and correlations for mass transfer coefficients in distillation operation available in the literature are used alongside the well known Fenske-Underwood-Gilliland equations and Billet-Schultz model of two-phase pressure drop for initial distillation column sizing. The most suitable kind of packing material and the associated design requirements are thereby ascertained through a simple computational model for meeting the stringent separation requirements of heavy water distillation.