ORNL CORROSION IN KRAFT DIGESTERS PROGRAM MODELLING UPDATE Project Review Meeting International Paper February, 2002

OUTLINE lModeling progress lKamloops digester lProblems fixed lSolid pressure lFuture work

DIGESTER MODEL lFinite volume lCurvilinear grids lBlock structured lTwo-phase: liquor flow, solid flow, temperature, delignification lSteady

RECENT PROGRESS lRe-evaluated inlet boundary conditions lReworked wall model lIdentified solid pressure problem - rechecked formulation and implementation lAddressed velocity profiles issues

Kamloops Digester BC

mm/s

VELOCITY PROFILES lSimulations produced large velocity profiles lFor two-phase, chips should not sense wall when a few chips diameters inside the digester lLiquid will follow the same profile as the chips lImprove wall treatment lLiquid should move slightly faster at wall

WALL BOUNDARY lPrevious calculations had no slip boundary lReplaced with - free slip - near free slip - relate to solid pressure and wet friction at wall lLooked at getting values for wet friction from PPC experiments lNeed confidence in solid pressure calculation

START OF SIMULATION lRemoved conical area as single phase region lStart calculation below chip level lEnsure input conditions corresponds to correlation's used lFixed over specification of problem - impose single pressure at top

SLIP AT INLET lReevaluation of inlet boundary conditions

SOLID PRESSURE lSolid pressure governed by - weight difference of chips and liquor - two-phase pressure drop lChecked density of each component as has large influence on buoyancy force (gravity force - buoyancy force) lIn 2D and 3D expect different values under the Can section as buoyancy force not as strong

SOLID PRESSURE lTesting of code and comparison with results in literature showed Ps to be low lBuoyancy term implemented in source term did not have effect lPrevious solid pressure at screen was removed lLine solver does not respond to high source term due to buoyancy term - related to convergence issue - needs to be solved lCalculated directly works

Next Step lSolve solid pressure solution problem lCheck delignification model lObtain full set calculation for Kamloops lObtain next set of conditions and perform second simulation - add 3D variations in BC lInterface results with ORNL boundary layer code