Chemical Cleaning - An Important Tool To Minimize Deposition-Related Boiler Tube Failures In Power Plants

摘要

Advancements in thermal power plants with higher ratings, specifically increased operating pressure and temperature, higher heat fluxes in boilers and cycles with higher thermal efficiencies have resulted in increased emphasis on equipment cleanliness. Over the last twenty years, substantial improvements have been made in the understanding and control of fossil plant cycle chemistry. In spite of these advances, waterside deposits in boiler tubes remain an issue of concern to many power plants. Deposits and/or scale within boiler tubes reduce heat transfer, creating an insulating barrier resulting in higher tube metal temperatures, which leads to accelerated material degradation by creep fatigue. In addition, the deposits also act as a location for the concentration of low level impurities present in the bulk boiler water up to significant corrosive levels at the deposit/tube interface. Depending on the nature of the concentrated impurities, different forms of damage occur - strong alkaline conditions lead to caustic damage and acidic conditions lead to hydrogen damage. Proper chemical cleaning decisions based on the nature of the failure, the type of boiler, the type of materials to be cleaned and the characteristics of the deposits have to be made to remove the deposits and thus minimize deposit-related boiler tube failures (BTF).