PURPOSE: To decrease remarkably the corrosion of a metallic wall by providing a heat insulating vessel to the inside of a nitric acid vessel made of metal, also providing both a heating means and a cooling means of a nitric acid soln. and keeping the metallic wall constituting the vessel at the specified temp. and below.
CONSTITUTION: A heat insulating vessel 2 is provided to the inside of a nitric acid vessel 1 made of metal and the heat insulating vessel 2 is constituted of such a heat insulating thickness that the outside is regulated to ≥80°C when the inside reaches b.p. of a nitric acid soln. 4. As the metallic walls 3 constituting the vessel 1, super low carbon austenite series 25 Cr steel or the like is used and ceramic or the like is used as the vessel 2. The outside of the vessel 1 is cooled with the cooling water 5 so that the metallic walls 3 are kept in ≤80°C and a heater 8 for heating it is inserted to the inside of the vessel 2. Since the temp. of the metallic walls 3 is kept in ≤80°C thereby, the corrosion due to nitric acid can be decreased.
KONO TAKAYUKI
ZAMA MASATO
OGURO TAKASHI
