PURPOSE: To prevent the deposition of scale on each cooling pipe by mechanical vibration and to maintain the performance of the cooler of a carbonating apparatus over a long term by arranging cooling pipes made of synthetic resin and having a small diameter while slackening central parts by ≥50mm in place of conventional cooling pipes made of metal.

CONSTITUTION: An aqueous soln. of Na2CO3 and gaseous CO2 are fed to a carbonating apparatus 1 provided with a multipipe type cooler 6 at the lower part from an upper inlet 2 and a lower inlet 3, respectively. The resulting NaHCO3 slurry is taken out of an outlet 4, and exhaust gas is discharged 5 from the top. In the cooler 6 many cooling pipes 7 made of synthetic resin are arranged while slackening central parts by ≥50, especially ≥200mm. The pipes 7 are preferably made of thermoplastic resin, especially fluororesin and are adjusted to 0.2W10mm outside diameter and 0.2W0.5mm thickness. By regulating the superficial velocity of gaseous CO2 blown from the lower inlet 3 during the operation of the apparatus 1 to ≥20m/hr, mechanical slight vibration is applied to the pipes 7 to prevent the deposition of crystals, that is, scale on the pipes 7.