PRODUCTION OF AN AROMATIC DICARBOXYLIC ACID

摘要

The present invention provides a process for the production of a purified aromatic dicarboxylic acid comprising the steps of: i) catalytically oxidizing a hydrocarbon precursor in an organic solvent to form a product stream and a vent gas in an oxidation stage; ii) separating the vent gas from the oxidation stage into an organic solvent-rich liquid stream and a water-rich vapour stream in a distillation stage; iii) condensing the water-rich vapour stream from the distillation stage into a condensate stream and a vapour stream in a first condensation stage by transferring heat from the water-rich vapour stream to a first coolant liquid flowing in a coolant system; and iv) forming a slurry of crude aromatic dicarboxylic acid crystals and an overhead vapour from the product stream from the oxidation stage in a crystallisation stage; and v) purifying the crude aromatic dicarboxylic acid crystals to yield the purified aromatic dicarboxylic acid, characterised in that the process further comprises the steps of: vi) condensing at least a portion of the overhead vapour from the crystallisation stage by transferring heat from the overhead vapour to a second coolant liquid flowing in the coolant system, wherein at least a portion of the second coolant liquid is derived from the first coolant liquid, wherein the condensing of at least a portion of the overhead vapour from the crystallisation stage is conducted in a second condensation stage comprising a first condenser; and vii) measuring the temperature of the second coolant liquid in the coolant system downstream of the first condenser and/or measuring the flow rate of the second coolant liquid in the coolant system; wherein the coolant system is configured to direct at least a portion of the second coolant liquid from a position in the coolant system downstream of the first condenser to a position in the coolant system upstream of the first condenser via a feedback system configured to cool the second coolant liquid if the measured temperature of the second coolant liquid downstream of the first condenser is greater than or equal to a first pre-set temperature and/or the measured flow rate of the second coolant liquid is less than or equal to a pre-set flow rate. The present invention further provides an apparatus for carrying out the process.