Continuous substituted aromatic hydrocarbon oxidation, acid crystallization and acid recovery system

Claim 1

IN THE PROCESS OF CONVERTING A POLYALKYL AROMATIC COMPOUND INTO AT LEAST ONE AROMATIC POLYCARBOXYLIC ACID PRODUCT IN THE PRESENCE OF A NORMALLY LIQUID MONOCARBOXYLIC ACID SOLVENT HAVING 2 TO 6 CARBON ATOMS PER MOLECULE WHEREIN SAID POLYALKYL AROMATIC COMPOUND IS CONTACTED WITH AN OXYGEN-CONTAINING GAS IN THE PRESENCE OF SUCH SOLVENT, AN OXIDATION CATALYST AND A BROMINE-AFFORDING SUBSTANCE IN AT LEAST ONE OXIDIZING ZONE AT AN AVERAGE TEMPERATURE IN THE RANGE OF ABOUT 325 TO 425*F. UNDER AVERAGE PRESSURE IN THE RANGE OF ABOUT 50 TO 500 P.S.I. WITH A CHARGING STOCK HOLDING TIME IN THE RANGE OF ABOUT .1 TO 3 HOURS, THE IMPROVED METHOD OF OPERATION WHICH COMPRISES COOLING OXIDATION ZONE EFFLUENT PRODUCT STREAM, REDUCING THE PRESSURE ON THE COOLED PRODUCT STREAM TO A LEVEL WHICH IS BELOW THE OXIDIZING PRESSURE BUT ABOVE ATMOSPHERIC PRESSURE AND HOLDING SAID STREAM IN A CRYSTALLIZING ZONE AT SAID REDUCED PRESSURE TO PERMIT THE GROWTH OF AROMATIC POLYCARBOXYLIC ACID PRODUCT CRYSTALS AND THEREBY OBTAIN A PRODUCT CRYSTAL SLURRY, REDUCING THE PRESSURE ON THE PRODUCT CRYSTAL SURRY WHILE INTRODUCING IT FROM SAID FIRST CRYSTALLIZING ZONE TO A SECOND CRYSTALLIZING ZONE WHICH IS AT SUBATMOSPHRIC PRESSURE, HOLDING THE SLURRY IN THE SECOND CRYSTALLIZING ZONE TO PERMIT FURTHER CRYSTAL GROWTH, CENTRIFUGING SAID SLURRY TO REMOVE MOTHER LIQUOR FROM CRYSTALS, AND CONTINUOUSLY WITHDRAWING VAPORS FROM AT LEAST ONE OF THE CRYSTALLIZING ZONES FOR EFFECTING BOTH CONCENTRATION AND REFRIGERATION OF LIQUID CONTAINED THEREIN.