Advanced Control of the Prehydrolysis Kraft Process


  • Aalto University Process Control and Automation Research Group
  • Aalto University Biorefineries Research Group
  • (SAPPI)



Begin: 2017-01-01

End: 2020-12-31



The ongoing trends in digitalization and environmental awareness have resulted in pressure for the traditional pulp and paper industry towards modernization of the biomass treatment processes for the production of novel bioproducts. The prehydrolysis kraft process adds an acidic pretreatment stage prior traditional kraft cooking cycle, which results in production of hemicellulose lean dissolving pulp that can be used for the production of textiles and various cellulose derivatives. In industrial applications, the prehydrolysis stage is conducted via autohydrolysis, where the naturally occurring acids in the wood, are catalyzing the hydrolysis reactions that are responsible for the removal of the hemicelluloses. Consequently, the variations in the raw material quality cause process disturbances, which require modifications on the cooking recipe.

A dynamic process model can be utilized for the development of improved control strategy that compensates the process disturbances, leading to e.g. improved yield, lower energy and material consumption, improved quality and reduced downtime. Several fundamental dynamic models have been developed for the unmodified kraft cooking process and the kinetics of the prehydrolysis stage have been studied extensively. However, no digester level model for the prehydrolysis kraft process has been published to date. This research aims for the development of a physico-chemical model of the prehydrolysis kraft process, which captures the dynamics of the entire digester system and the subsequent utilization of the acquired understanding for the development of an advanced optimization and control strategy.



Antton Lahnalammi


             This info last modified 2018-04-03 by Jukka Kortela