METHOD OF PRODUCING TEREPHTHALIC ACID

An object is to provide a method of terephthalic acid production in which slurry of crude terephthalic acid obtained through liquid-phase oxidation of a p-phenylene compound or a terephthalic acid slurry resulting from catalytic hydrogenation of the crude terephthalic acid is introduced into an upper part of a dispersion medium replacement tower while a second dispersion medium for replacement is introduced from a lower part of the dispersion medium replacement tower to perform dispersion medium replacement, the method capable of enabling the dispersion medium replacement tower to continue stable operation while maintaining an extremely high efficiency of dispersion medium replacement. A method of producing terephthalic acid, including the steps of: introducing starting terephthalic acid slurry into an upper part of a dispersion medium replacement tower, the starting terephthalic acid slurry containing a dispersion medium and crude terephthalic acid obtained through liquid-phase oxidation of a p-phenylene compound; bringing the starting terephthalic acid slurry into contact with an upward flow of a second dispersion medium introduced from a lower part of the dispersion medium replacement tower to form, in a lower compartment of the dispersion medium replacement tower, a layer of slurry of a purified terephthalic acid crystal dispersed in the second dispersion medium; discharging the slurry of the purified terephthalic acid crystal from the lower compartment of the dispersion medium replacement tower and delivering the slurry to a crystallization chamber provided with a unit for measuring slurry concentration; and delivering slurry in the crystallization chamber to a solid-liquid separation unit to separate a terephthalic acid crystal, wherein the following conditions (1) to (3) are maintained by regulating a flow rate of the second dispersion medium supplied to the lower compartment of the dispersion medium replacement tower, a flow rate of the slurry of the purified terephthalic acid crystal which is discharged from the lower compartment of the dispersion medium replacement tower, and a flow rate of the slurry delivered from the crystallization chamber to the solid-liquid separation unit: (1) volume V 1 of the slurry in the crystallization chamber is in a range of 0.050 to 0.80 times with respect to volume V 0 of the whole terephthalic acid slurry in the dispersion medium replacement tower; (2) a position of an interfacial region between the layer of the