METHOD OF PREVENTING TUBE OUTER SURFACE CORROSION FATIGUE CRACK OF COAL BURNING BOILER AND DAMAGE DIAGNOSTIC METHOD

摘要

PROBLEM TO BE SOLVED: To provide technologies for effectively preventing a water wall tube and an outer surface of a heat-transfer tube of a coal burning boiler from corrosion fatigue, and for precisely predicting the degree of the damage thereof.;SOLUTION: On sections such as the water wall tube of the boiler on which a repetitive thermal stresses act and on which coal ashes which show acidity in dissolving in water are mounted and deposited, when a boiler driving stopping period is equal to or more than the prescribed number of days (e.g. 4 days), if the temperature of the tube drops equal to or lower than a prescribed value (e.g. 50 degrees), or if the humidity thereof becomes equal to or higher than a prescribed value (e.g. at least 80 percent), a sulfuric-acid-corrosion-inhibitor-filled liquid constituted of an amine compound and the like is dispersed. Occurrence and development of corrosion fatigue cracks of the outer surface of the heat-transfer of the coal burning boiler and service life of the tube, are predicted from a function based on the pH of aqueous solution of adhesive coal ash, the concentration of easily decomposable nitrate, unburned carbon, the relative humidity during driving stopping, the number of days for driving stopping, and the number of repetition of the generation of the stress equal to or more than a prescribed amplitude value.;COPYRIGHT: (C)2003,JPO