Pulp Mill Corrosion and Wood Chip Extractives, 2006 Engineering, Pulping, & Environmental Conference

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Prior research shows that the corrosion rates of carbon steel equipment in the pulp mill can range from <0.03 mm/yr to >2.54 mm/yr, depending on process conditions and wood species pulped. 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 heartwood constituents during the pulping process. The current work investigates the impact of wood species and extractives on downstream process corrosion as a result of changes in the black liquor chemistry. Wood chips taken from two southeastern mills were evaluated for the impact of wood chip weathering and pre-extraction on pulp mill corrosion. Our research demonstrates the importance of operational parameters for wood species and wood chip usage and delivery to downstream process corrosion. Initial results indicate that an increase in corrosion of up to 50 times may be experienced in hardwoods and up to 3.5 times in softwoods.