Hydrogen fluoride purification

Claim 1

THE METHOD OF PROCESSING A LIQUID HYDROGEN FLUORIDE STREAM CONTAINING WATER WHICH CANNOT BE REMOVED THEREFROM BY SIMPLE DISTILLATION WHICH METHOD COMPRISES INTRODUCING SAID LIQUID AQUEOUS HYDROGEN FLUORIDE STREAM AT AN INTERMEDIATE LEVEL IN AN EXTRACTIVE DISTILLATION ZONE, INTRODUCING SULFURIC ACID OF ABOUT 90 TO 100 WEIGHT PER CENT CONCENTRATION AT THE UPPER PART OF SAID ZONE IN AN AMOUNT SUFFICIENT TO COMBINE WITH THE WATER CONTAINED IN THE INTRODUCED STREAM WITHOUT DILUTING THE SULFURIC ACID BELOW ABOUT 80 WEIGHT PER CENT, MAINTAINING SAID ZONE AT A PRESSURE OF ABOUT 5 TO 10 POUNDS PER SQUARE INCH GAUGE, MAINTAINING THE TOP OF SAID ZONE AT A TEMPERATURE IN THE RANGE OF ABOUT 80* TO 120* F., HEATING THE BOTTOM OF SAID ZONE TO MAINTAIN IT AT A TEMPERATURE IN THE RANGE OF ABOUT 300* TO 350* F., WITHDRAWING FROM THE TOP OF SAID ZONE AS ANHYDROUS HF SUBSTANTIALLY ALL OF THE HF INTRODUCED INTO SAID ZONE, AND WITHDRAWING FROM THE BASE OF SAID ZONE SULFURIC ACID OF AT LEAST ABOUT 80 WEIGHT PER CENT CONCENTRATION AND FREE FROM HF WHEREBY SAID WITHDRAWN SULFURIC ACID MAY BE CONCENTRATED BY REMOVAL OF WATER TO OBTAIN THE CONCENTRATED ACID FOR RETURN TO THE UPPER PART OF SAID ZONE.