Modeling Lime Kilns in

Pulp and Paper Mills

Process Simulations Ltd.#206, 2386 East Mall, Vancouver, BC, Canada

www.psl.bc.ca

August 23, 2006

Lime Kiln Issues

Kiln efficiency Lower fuel costs Burner characteristics Refractory life Dams and rings Stable operation

Primary AirSecondary Air Gas/Oil

Firehood

Burner

MotorChains

Limestone CaCO3Lime CaO

DRYINGZONE

CALCINING ZONE

BURNINGZONE

COOLINGZONE

Principle of ConservationMass

MomentumEnergy…….

IN = OUT

ININ

OUTOUT

OUTOUT

Computational Modeling

Build a real size kiln model Use computer to solve

equations Simulate processes in kiln

Mathematical Models for

Kiln Fully three-dimensional Reynolds-averaged transport equations of mass, momentum energy, and chemical species

Block-structure body-fitted coordinates with domain segmentation

Two-equation k-e turbulence model Ray tracing model for 3D radiation heat transfer

Gas combustion model Lagrangian solid fuel combustion models

Refractory and Calcination Models

Multi-layer refractory heat transfer model

Heat transfer and lime calcinationCaCO3 = CaO + CO2 Heat absorbed 1.679 MJ/kg CaCO3 @1089K

Modeling Output: Gas Velocity

0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50 52 54 56 58 60

Vmag[m/s]

Case 6

Modeling Output:

Gas Temperature400 500 600 700 800 900 1000 1100 1200 1300 1400 1500 1600 1700 1800 1900 2000 2100 2200 2300 2400 2500 2600 2700 2800 2900 3000

Tgas[F]

Case 6

Modeling Output:

Gas Species Concentrations

* Other species include CO, H2O, NOx, etc.

Modeling Output:

Flame Shape

0º

-5º

Modeling Output:

Refractory Temperature

Modeling Output:

Shell Temperature

Average Shell Temperature

0

50

100

150

200

250

300

350

400

0 30 60 90

Axial Distance (m)

T( C)

Model

Shell Scan

Modeling Output:

Kiln Axial Profiles

Distance from Kiln Hood [m]

Te

mp

era

ture

of

Ga

sa

nd

Lim

e[K

]

Vo

lum

eF

ract

ion

of

O2

,CO

2,H

2O

inF

lus

Ga

s[v

ol%

]

Em

issi

on

of

NO

inF

lue

Ga

s[p

pm

v]

Ma

ssF

ract

ion

of

Lim

eC

om

po

ne

nts

[wt%

]

0 20 40 60 80 100

50

01

00

01

50

02

00

0

0

5

10

15

20

25

30

35

40

01

00

20

03

00

40

05

00

0

10

20

30

40

50

60

70

80

90

100

Fe

ed

En

d

Fir

eE

nd

Tgas

CaCO3

CaO

Tck

NO

CO2

O2

H2O

Predicted Axial Profile Data

Modeling Output:

Gas Flow Animation

Modeling Output:

Solid Fuel Flow Animation

Value and Benefit of Kiln

Modeling Optimize burner design Optimize kiln performance Evaluate alternative fuels Minimize Emissions Identify and eliminate thermal hot spots

that lead to reduced brick lining lifetime Identify and fix problems with kiln

performance Improve waste gas incineration

Advantages of Kiln Modeling

Model provides comprehensive information throughout kiln at relatively low cost

Can evaluate “what if” scenarios to improve operation

Supplements operator knowledge of lime kiln operations

Assists mill managers in making decisions regarding kiln retrofits/replacements

Assists in optimizing burner and kiln designs

Modeling Application:

Burning Different Fuels

Heavy Oil

Petroleum Coke

Natural Gas

Modeling Application:

Oil/Gas Burner Design16" Sch40

OD: 0.4064mID: 0.3810m

12" Sch40OD: 0.3239mID: 0.3033m

8" Sch40OD: 0.2191mID: 0.2027m

6" Sch40OD:

0.1683m

4" Sch400.1143m

2-7/8" DIA0.073m

Spin Air

22 spinners, 30o

Axial AirAnnulus

Outer Swirl Gas24 Holes - 0.305"

Middle Axial Gas12 Holes - 0.5"

Inner Axial Gas12 Holes - 0.25"

Outer Oil Nozzle16 Holes - 3.18mm

Inner Oil Nozzle16 Holes - 4.76mm

16" Sch30OD: 0.4064mID: 0.3874m

12" OD; 1/4" thickOD: 0.3048mID: 0.2921m

8" Sch40OD: 0.2191mID: 0.2027m

8" Sch400.2027m

6" Sch400.1683m

4" Sch400.1143m

2-7/8" DIA0.073m

Spin Air22 Holes

Axial AirAnnulus

Outer Swirl Gas24 Holes - 0.305"

Middle Axial Gas12 Holes - 0.5"

Inner Axial Gas12 Holes - 0.25"

Outer Oil Nozzle16 Holes - 3.18mm

Inner Oil Nozzle16 Holes - 4.76mm

Modeling Application:

Coal Burner Design & NOx Emission

R1 R2

R3

Swirl Air20 vanes

groove width = 17.7 mmslot width =18.8 mm;

20 degrees

R0

R4

R5

R6

CoalTransport Air

Axial Air24 holes

18 mm Dia

R1

axial air24 slots0.0245 (1") wide 0.0130 (0.51") deep21 degrees inward

R2

R4

R3

R5

R0

Swirl airNo swirl

Transport air

Swirl Air20 vanes

groove width = 17.7 mmslot width =18.8 mm;

20 degrees

Modeling Application:

Direct & Indirect Coal Combustion

Axial Air

Coal Air

Axial Air

Coal Air

Swirl Air

Swirl Air

Coal Air

Coal Air

Modeling Application:

Burner with Different Primary Air

Oil Flame

@ Primary Air Ratio of 22%

Oil Flame

@ Primary Air Ratio of 60%

Primary Air

Swirl Angle: 45o

Direction same as kiln rotation

Primary Air

Swirl Angle = 0o

Oil Channel8 holes at 1/8" Dia.

Swirl Angle = 0o

Oil Channel12 holes at 3/16" Dia.

Swirl Angle = 0o

R1R3R2

R4

r2

r1

Modeling Application:

Burning NCG in Kilns

Case 2: NCG incineration with less HVLC

Case 3: NCG incineration with more HVLC

Case 4: No NCG incineration with less natural gas

Gas temperature on a vertical cross section

400 500 600 700 800 900 1000 1100 1200 1300 1400 1500 1600 1700 1800

Case 1: No NCG incineration with more natural gas

T [K]

Core Air

Natural Gas

Primary Air

Kiln Modeling Inputs: Overview

Site Survey and Measurements

Mass and Energy Balance Calculation

Kiln Geometry Refractory Lining Burner Design Lime Feed Properties Air Supplies DCS Data Analysis

Kiln Modeling Inputs:

Site Survey and Measurements

• Measured streams:

- air in

- fuel in

- flue gas out

- mud in

- product out

• Measured parameters:

- flow rate

- temperature

- composition

Kiln Modeling Inputs:

Example of Mass Balance

Mass In = Mass Out

Kiln Modeling Inputs:

Example of Energy Balance

Energy In = Energy Out

Kiln Modeling Inputs:

Kiln Geometry - Fire End

10' 6" Dia.

Barrel Tilt = 1.7899 = 3/8" per 12"o

Burner

4' 2 3/4"

24"24"

9"

5' 6"

2' 9"

17 3/4"

kiln c L

Z

X

Barrel Start(non rotated)

Kiln Modeling Inputs:

Kiln Geometry - Front View

Hood dimension, kiln diameter and length, tilt angle, kiln rotation

Location and size of any openings

Location and tilt angle of burner

15"

5' 3"

6' 7"

7' 3"

6 1/2"

4 1/2"

2 3/4"

2' 4 3/4"

15"

24" 12"

dia=?

24"

24"

2' 7/8"

15o

20" Dia.

Y

X

Kiln Modeling Inputs:

Kiln Burner Design

Primary Air

Swirl Angle: 45o

Direction same as kiln rotation

Primary Air

Swirl Angle = 0o

Oil Channel8 holes at 1/8" Dia.

Swirl Angle = 0o

Oil Channel12 holes at 3/16" Dia.

Swirl Angle = 0o

R1R3R2

R4

r2

r1

TOP VIEW

SIDE VIEW

BED_ANGLE 31 deg

BARREL_ANGLE 1.79 deg

BURNER_ANGLE_BETA 0.16 deg

BURNER_ANGLE_ALPHA 1.5 deg

SPIN_AIR_ANGLE 45 deg

R1 0.1138 m

R2 0.1626 m

R3 0.1869 m

R4 0.2154 m

Kiln Modeling Inputs:

Refractory Lining and Property

9"70% Alumina

9"Magnel RSV

9"70% Alumina

2-1/2"Greenlite HS

6"Clipper DP

3-1/2"Mix Refratherm

Greenlite

3"Greenlite HS

6"Castable

6"Castable

0' 0m

2'0.

6096

m

9.5'

2.89

56m

19.5

'5.

9436

m

39.5

'12

.039

8

84.5

'25

.755

6m

134.

5'40

.995

6m

216'

65.8

368m

221'

67.3

608m

226.

5'69

.037

2m

Burner

3'0.9144m

6"0.1524m

18"0.4572m

39"0.9906m

102"

2.59

08m

10'

3.04

8m

6' 7

"2.

0066

m

97"

2.46

38m

102"

2.59

08m

108"

2.74

32m

54'16.4592m

ChainSystem

101"

2.56

54m

012

23

34

4

4

0

aTaTaTaTaTaj

jj

thermal conductivity, W/mkT temperature, K

Material4a 3a 2a 1a 0a

Greenlite -2.554e-7 7.878e-4 5.248e-2Refratherm 150 -3.571e-7 8.021e-4 0.1576Magnel RSV 2.394e-12 -1.332e-8 2.771e-5 -0.02586 12.54Kruzite - 70 5.908e-7 -0.0013 2.301Clipper DP -3.571e-7 8.021e-4 0.1576

Kiln Modeling Inputs:

Kiln Lime Mud

1 8 o

0' 0m

2'0.6

096m 9.5

'2.8

956m

19.5'

5.9436

m 39.5'

12.039

8

84.5'

25.755

6m 134.5'

40.995

6m 216'

65.836

8m 221'

67.360

8m 226.5'

69.037

2m

B u r n e r10'3.0

48m

5 4 '1 6 . 4 5 9 2 m

C h a i nS y s t e m

15.6%

0.65m

11.35%

0.5207

m

10.09% 0.4

8m

9.04%

0.445m

8.29%

0.419m

Kiln Modeling Inputs:

Kiln DCS Data Display

Kiln Modeling Inputs:

Kiln Operational Data Analyzer

Selected Data Window

Kiln Modeling Inputs:

Selected Data Windows - 1

Kiln Modeling Inputs:

Selected Data Windows - 2

Kiln Modeling Inputs:

Computed Secondary Air Area

Kiln Modeling Inputs:

Averaged Mill DCS Data

Parameter Case 1

9/25/2003 8:30 to

10/2/2003 14:30

AIR

Primary Air Flow (kg/s) 1.28

Excess O2 (%) 1.34%

FEED

Dry Feed rate (kg/s) 6.14

Dust Losses (% dry feed) 10.8%

PRODUCT

CaO Production Rate (kg/s) 2.99

CaCO3 Remaining (% of Product) 1.86%

FUEL OIL

Fuel flow-crude tall oil (kg/s) 0.444

MISCELLANEOUS

Feed end draft (Pa) -535.1

Firing end draft (Pa) -124.1

Lime feed solids content 80%

Inerts (% of Product) 4%

AVERAGE DCS DATA

Time period for data average

SUPPLIED OR ESTIMATED DATA

Kiln Modeling Inputs:

Operation Conditions - Lime & Fuel

Production rate 274.42 tpd 3.1761 kg/sTotal feed rate 663.12 tpd 7.6750 kg/sSolids content 80% 80%CaCO3 462.23 tpd 5.3498 kg/sDust 57.29 tpd 0.6631 kg/sInerts 10.98 tpd 0.1270 kg/sMoisture 132.62 tpd 1.54 kg/s

663.12 tpd 7.6750 kg/s

Oil flow rate 0.4440 kg/sOil composition 100.00% Carbon 78.30% 0.3477 kg/s Hydrogen 9.88% 0.0439 kg/s

Oxygen 11.57% 0.0514 kg/s

Nitrogen 0.00% 0.0000 kg/s Sulphur 0.14% 0.0006 kg/s

Ash 0.11% 0.0005 kg/s High heat value 44.7040 MJ/kg Density 935.0 kg/m3

Oil temperature 230 oF 383 K

Stoichiometric air ratio for oil combustion 12.0178 kgAir/kgOilStoichiometric air for oil combustion 5.3359 kg/sAtomizing steam flow rate lb/hr 0.08 kg/sMixture flow rate 0.5240Mass fraction of oil in mixture 0.8473Total heat input 19.8 MW

LIME

FUEL

Kiln Modeling Inputs:

Operation Conditions - Air Supply

Excess air ratio 8.51%Stochiometric air flow rate*(1+excess air ratio) 5.7900 kg/s

PRIMARY AIR

Primary air flow rate 1.2800 kg/s

Primary air temperature 298.15 KPrimary air density 1.1835 kg/m^3Primary Axial Air 25.0% 0.3200 kg/sPrimary Spin Air 75.0% 0.9600 kg/s

SECONDARY AIRSecondary air temperature 298.15 KSecondary air density 1.1835 kg/m^3Left side flow area 0.2027 m*mRight side flow area 0.2027 m*mLeft side open area ratio 5.00%Right side open area ratio 5.00%Left side flow velocity 13.0334 m/sRight side flow velocity 13.0334 m/sLeft side flow rate 0.1563 kg/sRight side flow rate 0.1563 kg/s

BURNER/HOOD GAP AIRBurner/Hood gap air temperature 298.15 KBurner/Hood gap air density 1.1835 kg/m^3Burner/Hood gap area 0.0488 m*mBurner/Hood gap open area ratio 80.00%Burner/Hood gap velocity 13.0334 m/sBurner/Hood flow rate 0.6018 kg/s

DISCHARGE GRATE AIRDischarge grate air temperature 450 KDischarge grate air density 0.7841 kg/m^3Discharge grate area 0.5226 m*mDischarge grate open area ratio 54.80%Discharge grate velocity 16.0120 m/sDischarge grate flow rate 3.5956 kg/sTotal air flow rate 5.7901 kg/sTotal air flow rate - stochiometric air flow rate 0.0001 kg/s

Air

Kiln Modeling Inputs:

Flue Gas Calculation

speciesMolecular

WeightVolume % Mass %

H2O 2.0098 kg/s 18 31.3% 19.7%CO2 3.6287 kg/s 44 23.1% 35.6%O2 0.1044 kg/s 32 0.92% 1.02%N2 4.4583 kg/s 28 44.6% 43.7%

SO2 0.0012 kg/s 64 0.005% 0.012%Total 10.2024 kg/s 100.0% 100.0%

speciesMolecular

WeightVolume % Mass %

CO2 3.6287 kg/s 44 33.7% 44.3%O2 0.1044 kg/s 32 1.33% 1.27%N2 4.4583 kg/s 28 65.0% 54.4%

SO2 0.0012 kg/s 64 0.0% 0.015%Total 8.1926 kg/s 100.0% 100.0%

mass flow

True Flue Gas Calculation (dry based)

mass flow

True Flue Gas Calculation (wet based)

Gas Constant 287.15Ambient Pressure 101325PaAmbient Temperature 298.15KLoss Coefficient 0.9Firing End Draft -124.1Pakg/s to tpd (metric) 86.4

28 16 441 CO + 0.5*O2 = CO2

16 64 44 362 CH4 + 2*O2 = CO2 + 2*H2O

2 16 18

3 H2 + 0.5*O2 = H2O

12 32 444 C + O2 = CO2

100 44 56

5 CaCO3 = CO2 + CaO

14 16 306 N + 0.5*O2 = NO

32 32 647 S + O2 = SO2

Species Reactions (with molecular weights)