Heat exchange process

Claim 1

AN IMPROVED PROCESS OF COOLING THE REACTION PRODUCT MIXTURE COMPRISING PIGMENTARY TITANIUM DIOXIDE AND BY-PRODUCT CHLORINE AND HYDROGEN CHLORIDE FROM THE CONTINOUS VAPOR PHASE OXIDATION OF A TITANIUM TETRACHLORIDE WITH AN OXYGEN-CONTAINING GAS, COMPRISING CHARGING SAID MIXTURE AS A STREAM INTO A TUBULAR, INDIRECT HEAT EXCHANGE ZONE WHILE AT A TEMPERATURE RANGING FROM 800*C. TO 1400*C., TOGETHER WITH FROM ONE-HALF TO TEN PARTS BY WEIGHT PER HUNDRED PARTS OF PIGMENTARY TITANIUM DIOXIDE OF INERT SOLID CARBON DIOXIDE IN PARTICULATE FORM TO MAINTAIN THE INTERNAL SURFACES OF SAID ZONE SUBSTANTIALLY FREE OF DEPOSITED, COMPACTED TIO2 SOLIDS, COOLING SAID GAS CONVEYED STREAM OF TITANIUM DIOXIDE TO A TEMPERATURE WITHIN THE RANGE OF ABOUT 25-150*C., AND SUBSTANTIALLY COMPLETELY VAPORIZING SAID PARTICULATE CARBON SIOXIDE DURING PASSAGE OF THE MIXTURE THROUGH SAID ZONE, AND THEREAFTER RECOVERING THE RESULTING COOLED, CONTAMINANTFREE PIGMENTARY TITANIUM DIOXIDE.