Corrosion During Acid Cleaning, Kraft Digesters and Evaporators

Kraft digesters and evaporators in North America are typically acid-cleaned to remove scales that precipitate from chemical species present in liquors. Such scales do not cause corrosion, but their removal with acid may compromise the base metal on which they grow. Cleaning can lead to localized corrosion and unexpected equipment failures. The objective of this research is to determine optimal cleaning practices for kraft digesters, evaporators and other equipment during scheduled shutdowns. The overall goal of this research is to minimize corrosion (metal loss) during scale removal, but the research will also measure cleaning cost-effectiveness and identiry environmental and safety concerns during cleaning.