Modelling of the Chemical Reactions in a Continuous Pulping Digester in the Presence of the Channelling Phenomenon

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The objective of this paper is to predict the chemical and hydraulic behaviour of the pulping digester under hazardous conditions which include the channelling phenomenon. The pulping digester was modelled using the CFD, finite volume method in FLUENT, including the channelling phenomenon and chemical reactions in the channel. A 2D geometry of the digester was built and symmetric planes were defined in Gambit. The mesh was then exported to the FLUENT and the geometry was treated with the axisymmetric function to establish a complete model of the digester. The Eulerian scheme was applied to represent the multiphase flows in the digester. A heterogeneous porous media was defined for the compressible bed. Species transport was applied to define a mixture template of the wood chips components. The Kappa number was predicted in and around the channel to characterize how cooking develops under hazardous conditions.
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Pulping Digester; Channelling; Mass Transfer; Lignin; Chemical Reaction; Porous Media; Multiphase; Axisymmetric

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