METHOD FOR CLEANING AND PASSIVATION OF INNER SURFACE OF BOILER TUBES WITH SUCCESSIVE EXPOSURE TO CHEMICAL AGENT AND WATER-OXYGEN MIXTURE Russian patent published in 2014 - IPC F28G9/00 

FIELD: chemistry.

SUBSTANCE: disclosed is a method of cleaning the inner surface of boiler tubes via treatment thereof in a separate loop with a hot water-based cleaning medium with addition of a chemical agent in form of an aqueous solution of a disodium salt of ethylenediaminetetraacetic acid. Said hot medium is boiler water at temperature of 90-100°C; the aqueous solution of said chemical agent is added to said medium for 40-80 minutes until achieving concentration thereof in the boiler water of 1.0-1.2 wt % at pH=5.0-6.0. Post-treatment and passivation of the inner surface of the boiler tubes is then carried out by switching to boiler operation in starting conditions while raising pressure and temperature of the boiler water at pH=8.8-9.3 to 3.0-25.0 MPa and 150-420°C, respectively, and feeding oxygen with concentration of 1.8-2.2 g/dm³ into the boiler water for 9-12 hours and gradually removing said chemical agent from the treated loop for 40-80 minutes.

EFFECT: high reliability of operation of explosion-proof devices in case of accidental explosion at a facility and reduced release of hazardous substances into the atmosphere.

3 dwg, 3 tbl