A Data-driven Approach to Automated Grade Transitions for Pulp Mill, TAPPICon26

Grade changes in a pulp mill are operationally challenging and often result in significant inefficiencies. The primary challenges include increased off-spec production due to delayed or inaccurate manual adjustments across equipment with long process delays, and incorrect chemical dosages that adversely affect product quality. This study addresses these challenges by implementing a robust tracking mechanism that provides real-time traceability across the fiber line, including digesters, bleaching sections, and high-density (HD) storage towers. By employing dynamic mass and component balance models, the system calculates the "twilight zone” the transitional region of mixed pulp properties—allowing for precise coordination of chemical dosages and grade boundaries.

Results from an industrial implementation in a European kraft pulp mill demonstrate significant potential to reduce off-spec pulp production by automating grade transitions. Furthermore, optimized chemical dosages based on precise pulp movement can reduce chemical consumption during transition events. This paper details the mathematical modeling of pulp movement, and the operational shifts from reactive to proactive grade management. The findings suggest that pulp traceability and tracking is a prerequisite for autonomous fiber-line operation and a significant driver of mill-wide profitability.

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