Hydrogen fluoride process

Claim 1

PROCESS FOR PRODUCING PURE ANHYDROUS HYDROGEN FLUORIDE COMPRISING REACTING CALCIUM FLUORIDE AND SULFURIC ACID, RECOVERING AN IMPURE GAS STREAM CONTAINING HYDROGEN FLUORIDE TOGETHER WITH ENTRAINED SOLIDS, MIST, AND GASEOUS IMPURITIES INCLUDING WATER VAPOR, SULFUR DIOXIDE AND INERT GAS, FILTERING AND SCRUBBING SAID GAS STREAM FOR SOLIDS AND MIST REMOVAL, COOLING SAID GAS STREAM TO A TEMPERATURE BETWEEN ABOUT 67*F. TO 72*F. WHEREBY PARTIAL CONDENSATION RESULTS, RECYCLING LIQUID CONDENSATE TO SAID SCRUBBING, FURTHER PARTIALLY CONDENSING AND DISTILLING THE RESIDUAL GAS STREAM IN A FIST DISTILLATION ZONE TO PRODUCE AN OVERHEAD WASTE GAS STREAM AT A TEMPERATURE BETWEEN ABOUT 65*F. TO 67*F. CONTAINING GASEOUS INERTS, AN AQUEOUS LIQUID BOTTOMS STREAM AT A TEMPERATURE BETWEEN ABOUT 70*F. TO 75*F. AND AN INTERMEDIATE LIQUID PROCESS STREAM, COOLING AND REFLUXING SAID OVERHEAD GAS STREAM TO RECOVER HYDROGEN FLUORIDE CONTENT, DISCHARGING THE RESIDUAL INERTS-LADEN GAS STREAM, RECYCLING SAID AQUEOUS LIQUID BOTTOMS STREAM TO SAID SCRUBBING STEP, WITHDRAWING SAID INTERMEDIATE LIQUID PROCESS STREAM AT A TEMPERATURE BETWEEN ABOUT 63*F. TO 68*F. FROM A STAGE OF SAID DISTILLATION STEP ABOVE THE ENTRY OF SAID RESIDUAL GAS STREAM AND BELOW THE RECYCLE OF OVERHEAD GAS STREAM REFLUX WHEREBY SAID INTERMEDIATE LIQUID PROCESS STREAM IS RECOVERED SUBSTANTIALLY FREE OF IMPURITIES OTHER THAN UP TO ABOUT 2% SULFUR DIOXIDE, SEPARATELY FURTHER DISTILLING SAID INTERMEDIATE LIQUID PROCESS STREAM IN A SECOND DISTILLATION ZONE TO PRODUCE AN OVERHEAD GAS STREAM CONTAINING SULFUR DIOXIDE AND A LIQUID BOTTOMS STREAM, COOLING AND REFLUXING SAID OVERHEAD GAS STREAM TO RECOVER HYDROGEN FLUORIDE CONTENT, DISCHARGING THE RESIDUAL SULFUR DIOXIDE-LADEN GAS STREAM, AND RECOVERING SAID LIQUID BOTTOMS STREAM OF PURE HYDROGEN FLUORIDE PRODUCT AND SUBSTANTIALLY FREE OF SULFUR DIOXIDE AND WATER.