Method of refining benzoic acid

A process for purifying benzoic acid comprising:

• introducing, into a continuous crystallization apparatus equipped with a stirrer and a heating device, crystals of crude benzoic acid with a bulk density controlled at 0.2 g/cm3 or more and an average particle diameter of 0.3 mm or more, from an upper portion of said apparatus;
• effecting purification by counter-current contact of the crystals of crude benzoic acid falling through inside of the apparatus with a melt generated by heating with said heating device, wherein said purification is effected by repeated dissolving and crystallizing of benzoic acid as it falls through said apparatus and wherein a temperature gradient exists in said apparatus from a low temperature at the top of said apparatus to a high temperature at the bottom of said apparatus;
• withdrawing purified benzoic acid as melt from a lower portion of the apparatus;
• and
• withdrawing mother liquor from the upper portion of the apparatus.