Vacuum distillation of liquid metals: Part I. Theory and experimental study

The kinetics of vacuum distilling copper, tin, manganese, and sulfur from melted steel scrap have been measured. The experiments found that 70 to 90 pct of initial copper, 60 to 80 pct of initial tin, 80 to 100 pct of initial managanese, and 20 to 40 pct of initial sulfur can be eliminated in 30 minutes exposure to vacuum. Melt masses were in the range 10 to 60 kg, melt temperatures in the range 1850 to 2050 K, and chamber pressures in the range 3 to 400 pascals. Crucible diameter was 0.2m. Mass transport has been described in terms of Machlin's model for melt phase diffusion, Langmuir's model for evaporation, and convective bulk flow for gas phase mass transport. Two preliminary criteria are shown to demonstrate the suitability of vacuum distillation to any particular system and a third operational criterion is developed to define the range of vacuum required to eliminate gas phase mass transport resistance effectively. W.G. Davenport formerly with McGill University