Efficiency of Multiple Distillation or Crystallization Refining with a Preset Yield

Abstract—

For an impurity with a separation factor β < 1, we compare calculated average impurity concentrations (C_n/C₁) in products of multiple- and single-cycle distillation or directional solidification refining processes with a preset final yield. The n-fold process with a yield g in each cycle and a final yield G = gⁿ is shown to be more efficient than a single-cycle process with the same final yield G. Each new cycle of the process is less efficient than the preceding one. At a given G, the relative efficiency of the n-fold process rises with an increase in the deviation of β < 1 from unity and with increasing n (with the corresponding increase in g = G^1/n). Examples are presented of C_n/C₁ calculation at high values of G.