Preliminary Evaluation of Evaporator Fouling: A Comparison of AQ and Non-AQ Liquors, 1998 Pulping Conference Proceedings

As the pulp and paper industry moves toward improving efficiency in a pulp mill it becomes necessary to maximize available resources. Extension of the digester yield through the use of Anthraquinone, which catalyzes the digestion of the pulp and improves the performance of the cooking process, is one of the common ways to improve productivity. However, any changes in the pulping process which lead to alterations in the existing black liquor chemistry may increase fouling in the evaporator train.

The two liquors, one collected while AQ was in use and the other one while AQ was not, were generated at the same bleached kraft mill. This work examined the differences in composition, rheology, scaling tendency, and scale composition between these two liquors. Compositional analysis of the two liquors indicates that there is a difference in the scaling tendency between them. This was further confirmed by multiple experiments on a 0.06 m 2 bench-top falling film evaporator. The scaling rate of the liquor generated during the use of AQ was greater than the scaling rate of the “normal” liquor in our bench-top evaporator. Further research on a larger pilot scale is required to confirm and extend these results.