Removal of hf from an hf-containing gas

Abstract

Abstract HF IS REMOVED FROM A HF-CONTAINING GAS BY SCRUBBING THE GAS WITH WATER, WHEREBY THE HF FROM THE GAS ENTERS THE AQUEOUS PHASE TO FORM AN AQUEOUS SOLUTION OF NF, AND THE GAS PHASE IS VENTED AS VIRTUALLY HF-FREE GAS. PRECIPITATION OF THE FLUORIDE ION IN THE AQUEOUS SOLUTION AS CAF2 IS CARRIED OUT BY ADDING CA(OH)2, CACO3, OR A MIXTURE THEREOF TO THE SOLUTION. SETTLING OF THE PRECIPITATE IS IMPROVED BY ADDING CASO4 TO THE AQUEOUS SOLUTION DURING THE REACTION FORMING THE PRECIPITATE. THE RESULTANT PRECIPITATE IS READILY FILTERABLE FROM THE AQUEOUS PHASE. THE AQUEOUS PHASE WHICH REMAINS IS VIRTUALLY HFFREE AND CAN BE REUSED FOR SCRUBBING HF-CONTAINING GAS. THE NEUTRALIZATION REACTION WHICH ACCOMPANIES ADDITION OF THE CA(OH)2 OR CACO3 TO THE AQUEOUS SOLUTION CAN BE CARRIED OUT IN TWO STEPS, FIRST TO PARTIALLY NEUTRALIZE THE SOLUTION, E.G. PH UP TO 6 SO THAT THE SOLUTION IS STILL ABLE TO BE PUMPED TO A SETTLING TANK FOR EXAMPLE, AND SECOND TO COMPLETE NEUTRALIZATION IN THE SETTLING TANK. THE CASO4 ADDITION CAN BE POSTPONED UNTIL ADDITION OF CA(OH)2, CACO3 OR MIXTURE THEREOF TO THE SETTLING TANK.

Inventors

• 👤 N West

Bibliographic Details