The Behavior of Sodium Sulphite in High-Pressure Steam Boilers

Abstract

Abstract 1 Tests for sulphite and sulphite in condensed steam and for sulphide in boiler water are described, which tests are sensitive to 0.01 ppm as sulphur. 2 By these tests, it was found that no hydrolysis of sodium sulphite occurs up to a boiler pressure of 1775 lb per sq in. 3 Tests on water in boilers operating at 675 and 1400 lb per sq in. pressure showed no auto-oxidation and reduction of sodium sulphite in such waters. Tests on a third boiler, carrying a pressure of 1775 lb per sq in., showed slight traces of such a reaction. The slowness of sulphite consumption in the three boilers precludes any significant auto-oxidation and reduction at the metal surfaces. This is opposed to certain laboratory data which indicate that this reaction is of the first order and rapid at high temperatures. 4 Of the small amounts of sodium sulphite carried into the steam mechanically, a portion decomposes to sulphate and sulphide as the spray of water becomes concentrated or dried. The amounts present, however, are too small to be of significance. 5 In view of these findings, it is the authors’ conclusion that sodium sulphite can be used in high-pressure boilers with no harmful effects. 6 A continuous feed to maintain 10 to 20 ppm sodium sulphite in the boiler water is recommended.