www.amerflowtec.com

CFD MODELING OF PULP & CFD MODELING OF PULP &

PAPER KILNSPAPER KILNSE. Bibeau and K. AdaneE. Bibeau and K. Adane

2006 CFD SummitMay 22-24, 2006 - Monterey, CA

AFT BackgroundAFT BackgroundServices

Modeling CFD ServicesHelp clients for development of engineered systems and in users of equipment faced with complex problems

BenefitsEnhanced Engineering JudgementHardware design solutionsIntegration of CFD in design process

CFD in IndustryCFD in IndustryAdvantages

Technical risks reductionLessen project uncertaintyEnvironmental complianceDecrease energy costsImprove the commissioning phaseImprove equipment performanceEvaluate proposed changesCan evaluate “what if” scenarios

Lime KilnsLime Kilns

Key Issues Lime KilnsKey Issues Lime KilnsKiln efficiencyFuel substitutionBurner characteristicsFlame shape/positionOptimal swirl numberReduce energy costsEmissions: NOx, SOxRefractory life

Model PredictionsModel PredictionsEffect of burner and settingsFlame shapeHeat release profile to productHood shape and air ports influencePrimary/Secondary/Fuel ratio influenceGas species (H2, O2, N2, CO, CO2, H2O, CH4)Pollutant emissions (e.g. NOx)Oil or solid fuel (tires, coke, coal) combustion and droplet trajectoryMud, refractory, and shell temperatures

Lime KilnsLime KilnsBurner (combination)– atomizing oil + steam– coal and coke solid fuel – natural gas– non-condensable gases– alternative energy fuels (biogas, waste polymers)

Primary air– via burner and used for conveying solid fuel

Secondary air– induced air through various kiln air ports– air leakage from seal gap, camera ports, side hood port,

and back hood ports

Comprehensive Input Condition ModelComprehensive Input Condition Model

EXCEL

DATA INPUT ANDRITZ

CFD

Parametric Mesh Generation Using Parametric Mesh Generation Using Gambit for Gambit for ““what ifwhat if”” senriossenrios

/case 9: calcinations kiln Andritz. New SA and lance and 6 holesresetsolver select "FLUENT 5/6"

$imesh = 5$scale1 = 1.0$ilance = 1

default set "MESH.INTERVAL.SIZE" numeric 0.1

/kiln$l1 = 0.6096$l2 = $l1 + 0.3048$l3 = $l2 + 2.24$l4 = $l3 + (15.14 + 12.19)*$scale1$r4 = 3.708/2$r3 = 1.651$r2 = 1.588$r1 = 0.991$r0 = 0.750

/air seal$gap1 = 0.0127$gap3 = 0.0254

/grate$grate_xo = -0.333$grate_yo = 22*0.0254$grate_x = (2*12+2.5)*0.0254*0.80$grate_y = (3*12+4.5)*0.0254*0.80

/shell distance from hood$gap2 = $l3

volume create "kiln" height ($l1) radius1 ($rh-$gap1) radius3 $r1 offset ($l1/2) 0 0 xaxis frustumvolume create "k2" height ($l2-$l1) radius1 $r1 radius3 $r1 offset (($l2-$l1)/2+$l1) 0 0 xaxis frustumvolume create "k3" height ($l3-$l2) radius1 $r1 radius3 $r2 offset (($l3-$l2)/2+$l2) 0 0 xaxis frustumvolume create "k4" height ($l4-$l3) radius1 $r2 radius3 $r2 offset (($l4-$l3)/2+$l3) 0 0 xaxis frustumvolume unite volumes "kiln" "k2" "k3" "k4" volume create "shell" height ($l4-$gap2) radius1 $r4 radius3 $r4 offset (($l4-$gap2)/2+$gap2) 0 0 xaxis frustumvolume split "shell" volumes "kiln" connected bientityvolume unite volumes "kiln" ("volume."+ntos(LASTID(4)-1))

face create "ring1" width (5) height (5) offset (0) (5/2) (0) yzplane rectangleface split "face.34" connected face "ring1"face create "ring2" width (5) height (5) offset (-$gap3) (0) (0) yzplane rectangleface split "face.31" connected face "ring2"

IF COND ($imesh .gt. 1)$l2plus = $l2volume create "mud" width ($l4-$l2plus) depth 5 height 2 offset (($l4-

$l2plus)/2+$l2plus) 0 (-2/2-$h_mud) brickvolume move "mud" dangle (-90.0-$angle) vector 1 0 0 origin 0 0 0

connectedvolume subtract "kiln" volumes "mud" keeptoolvolume subtract "shell" volumes "mud"

volume create "burner" height ($lb+0.5) radius1 $rb11 radius3 $rb11 offset ($lb/2 -$lh - 0.5/2) 0 0 xaxis frustum

volume move offset (0.0+$lh) 0 0

Kiln Geometry ExampleKiln Geometry ExampleTop holes 5 and 6

Lower leakage ring

Upper leakage ring

Grate

Middle holes 4 and 5 with burner leakage

Dam area with throat sectionBurner & Lance

Kiln with bricks

Lime bed

Unstructured body-fitted coordinates with both hexa and tetra elements (GAMBIT)

Numerical DescriptionsNumerical Descriptions

Sample Mesh of the Kiln

Fully three-dimensional Reynolds-averaged transport equations of mass, momentum energy, and chemical speciesTwo-equation k-e turbulence modelDiffusion equation for 3D radiation heat transferRefractory wall modelSeparate sub-models for drying, devolatilization, and char combustion for the cokeNOx formation model

Numerical DescriptionsNumerical Descriptions

CmHn+ (m + 0.25n)O2= mCO2 + 0.5n H2O

CO+0.5O2 = CO2

H2+0.5O2 = H2O

Arrhenius-reactions kineticsGas combustion–controlled by turbulent diffusion (Magnussen eddy-dissipation Model)

Swirl number

Numerical DescriptionsNumerical Descriptions

eqCokeAirInnerNGOuterNGimaryAirOuter

gAirimarySwirlInner

DvmvmvmvmRvm

])()()()[()45sin()(

Pr

Pr

&&&&

&

+++

Operational ParametersOperational ParametersHeat input via combination of fuels– 20 to 40 MW typical range– depends on market price and availability of alternative

fuelsFuels– gas, oil, coke, biogas, polymers

Port openings– Various strategies to influence flame/hood interactions

Decrease thermal NOx formationPrevent high temperatures that contribute to premature brick failuresNCG burning: interaction with main flameBurner tilt

Simulation ResultsSimulation Results

Streamlines

OIL & COKE

Oil/CokeOil/Coke

Oil/Coke

Comparison to 1Comparison to 1--D ModelsD Models

gMass fraction of c19h30 Mass fraction coke volMass fraction of o2 Mass fraction of CO Mass fraction of co2 Mass fraction of H2Mass fraction of CH4Mass fraction of n2 Mass fraction of C(s)Mass fraction of S(s)Mass fraction of h2o Mass fraction of so2

CFDAveraged

Values

Overall mass balance 1-D

models (IDEAS)

Temperature Velocity vectors

NGNG/Coke/Coke

NG & COKENG & COKE

NG/NG/CokeCoke

Effect of CoEffect of Co--firingfiringNG/Coke

NG/Coke

Temperature (K)Lance

Coke SubstitutionCoke Substitution

NG/Coke

NG/Coke

Temperature (K)

Oil/NG

Oil/NG

Oil/NG

OIL & NG

NONOxx

Emissions

Consultants/Andritz

Permits

CFD

Kiln

Emission Data

Regulation

OIL & COKE

SOSO22/O/O22

Oil/Coke Oil/Coke

Oil/Coke

Effect of SwirlEffect of SwirlSwirl = High

Swirl = Low

Temperature (K)

Effect of SwirlEffect of SwirlSwirl = High Swirl = Low

Temperature (K)

Effect of Swirl of BurnerEffect of Swirl of Burner

Swirl = High

Swirl = Low

Velocity Magnitude (m/s)

ConclusionConclusionUse CFD to support emission permit processUse CFD to optimised burner chamber interactions Model NOx and SO2 formation in kilns to aid burner designSwirl number is important for both burner design and operations.

AcknowledgmentAcknowledgment

Andritz – Burner studies and designsUniversity of Manitoba– CFD simulations of alternative

energy

www.amerflowtec.com