PROCESS simulated both a double-effect evaporator and packed distillation tower for regenerating (concentrating) a hydrochloric acid stream. The software thermodynamics package was used to predict the shift in the HCl/water azeotrope caused by the presence of antimony trichloride. PROCESS was able to show that the operating envelope for the preferred (from an energy consumption standpoint) evaporation system was far too small for practical process control. The selected distillation system process design was then completed (required number of theoretical stages, HETP, optimum column diameter, and reboiler size) using the software. Additional simulation cases were quickly run to determine designed distillation column performance under various postulated operating conditions.