Pulping digester including the channelling phenomenon and chemical reactions in the channel is modelled using the CFD, finite volume method, FLUENT. The objective of this paper is to predict the chemical and hydraulic behaviour of the digester under the hazardous situations.

A 2D geometry of the digester is built and symmetric planes are defined in the Gambit. The mesh is then exported to the FLUENT and then the created half geometry was treated by axisymmetric function to establish a complete model of the digester. The Eulerian scheme is applied which    represent the multiphase flows in the digester. A heterogeneous porous media is defined for the compressible bed. Species transport is applied to define a mixture template of the wood chips components. The kappa number is predicted in the channel and around it to characterize the cooking development under hazardous conditions.