Hydrogen chloride recovery and purification from gases containing hydrogen fluoride

Claim 1

A CONTINUOUS PROCESS FOR RECOVERY OF SUBSTANTIALLY PURE ANHYDROUS HYDROGEN CHLORIDE FROM A GASEOUS MIXTURE CONTAINING A SUBSTANTIAL PORTION OF HYDROGEN CHLORIDE AND A RELATIVELY SMALL AMOUNT OF HYDROGEN FLUORIDE, WHICH COMPRISES SCRUBBING SAID MIXTURE IN AN ACID ABSORBER WITH A RECYCLED STREAM OF DILUTE HYDROCHLORIC ACID SCRUBBING SOLUTION TO FORM A SUBSTANTIALLY SATURATED AQUEOUS ACID SOLUTION, PASSING SAID LATTER ACID SOLUTION THROUGH A HEATED STRIPPER FROM WHICH A PORITON OF THE ACID IS RECOVERED AS AN OVERHEAD PRODUCT IN THE FORM OF SUBSTANTIALLY ANHYDROUS, HYDROGEN FLUORIDE-FREE HYDROGEN CHLORIDE AND THE REMAINING PORTION IS REMOVED AS STRIPPER BOTTOMS PRODUCT CONTAINING HYDROGEN FLUORIDE, REACTING THE HYDROGEN FLUORIDE IN SAID BOTTOMS PRODUCT IN A SEPARATE VESSEL AT A TEMPERATURE OF AT LEAST 55*C. WITH SUFFICIENTLY LESS THAN A STOICHIOMETRIC AMOUNT OF CALCIUM CHLORIDE SO THAT THE HYDROGEN FLUORIDE CONTENT OF THE BOTTOMS PRODUCT AFTER REACTION WITH SAID CALCIUM CHLORIDE IS NOT REDUCED BELOW ABOUT 1.0% BY WEIGHT OF THE REACTED BOTTOMS PRODUCT, THEREBY CAUSING PRECIPITATION OF CRYSTALS OF CALCIUM FLUORIDE IN FIL TERABLE FORM FROM SAID REACTED BOTTOMS PRODUCT, SEPARATING SAID CRYSTALS FROM THE MOTHER LIQUOR BY FILTERING, AND RECYCLING A PORTION OF SAID MOTHER LIQUOR TO THE ABSORBER.