Patent ID: 8512447

Claim:
A method for purifying a chlorine supply comprising a chlorine component, a bromine component, and nitrogen trichloride in a distillation system to form purified chlorine gas having less than 20 parts by weight of the bromine component per one million parts by weight of the purified chlorine gas and to form a distillate comprising liquid chlorine and the bromine component, wherein the distillation system is fluidly connected to a vaporizer and comprises a distillation tower that has an upper end and a lower end, a vertical axis extending through the upper and lower ends, and a vapor-liquid contact device to provide a vapor-liquid interface between a vapor and a condensate, a reflux condenser that is in fluid communication with the upper end of the distillation tower, disposed above the distillation tower, and that shares the vertical axis with the distillation tower, and wherein the distillation system also comprises a reboiler disposed below the distillation tower and in fluid communication with the lower end of the distillation tower, said method comprising the steps of: A. introducing the chlorine supply into the vaporizer; B. heating the chlorine supply to a temperature of from 50° C. to 120° C. in the vaporizer to form the vapor; C. introducing the vapor into the distillation system to provide purified chlorine gas, a distillate comprising the liquid chlorine and the bromine component, and a bottoms component comprising the nitrogen trichloride; D. condensing the vapor in the reflux condenser to form the condensate which flows from the reflux condenser into the upper end of the distillation tower such that the condensate interacts with the vapor at vapor-liquid contact device thereby forming the purified chlorine gas and the distillate; E. heating the condensate in the reboiler; F. removing the purified chlorine gas from the distillation system; and G. removing the distillate from the distillation system.