Role of wood extractives in black liquor corrosiveness

Abstract In the pulp and paper industry, variability in the process and wood source may result in highly corrosive waste liquors, called black liquors, from the Kraft pulping process. Prior research has demonstrated corrosion rates of carbon steel in pulp mill equipment ranging from 2.54 mm/y, depending on the wood species pulped. In this study wood species-dependent corrosion is confirmed and age-dependent corrosion is investigated as a function of organic extractive content. The composition of the organic portion of black liquor depends largely on the wood species used. Organic components come from extractives in the wood chips or are generated from the degradation of lignin and other wood constituents during the pulping process. Depending upon the wood species used, some black liquor constituents have been identified to increase the corrosiveness of black liquors whereas others may act as corrosion inhibitors. Our research demonstrates the importance of operational parameters for wood sp...