limekiln modeling.ppt

8/11/2019 LimeKiln Modeling.ppt

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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


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Lime Kiln Issues

Kiln efficiency Lower fuel costs

Burner characteristics

Refractory life

Dams and rings Stable operation

Primary Air

Secondary Air Gas/Oil

FirehoodBurner

MotorChains

Limestone CaCO3

Lime CaO

DRYING

ZONE

CALCINING

ZONE

BURNING

ZONE

COOLING

ZONE


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Principle of ConservationMassMomentum

Energy

.

IN = OUT

IN

OUT

OUT

Computational Modeling

Build a real size kiln model

Use computer to solve

equations

Simulate processes in kiln


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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- turbulence model

Ray tracing model for 3D radiation heat

transfer

Gas combustion model

Lagrangian solid fuel combustion models


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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


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Modeling Output:

Gas Velocity

0 2 4 6 8 10 1 2 14 1 6 18 2 0 22 2 4 26 2 8 30 3 2 34 3 6 38 4 0 42 4 4 46 4 8 50 5 2 54 5 6 58 6 0

Vmag[m/s]

Case 6


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Modeling Output:

Gas Temperature

400 500 600 700 800 900 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


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Modeling Output:

Gas Species Concentrations

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


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Modeling Output:

Flame Shape

-5


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Modeling Output:

Refractory Temperature


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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


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Modeling Output:

Kiln Axial Profiles

Distance from Kiln Hood [m]

TemperatureofGasandLim

e[K]

VolumeFrac

tionofO2,

CO2,

H2OinFlusGas[vol%]

EmissionofNOinFlueGas[ppmv]

MassF

ractionofLimeCompone

nts[wt%]

0 20 40 60 80 100

500

1000

1500

2000

0

5

10

15

20

25

30

35

40

0

100

200

300

400

500

0

10

20

30

40

50

60

70

80

90

100

FeedEnd

FireEnd

Tgas

CaCO3

CaO

Tck

NO

CO2

O2

H2O

Predicted Axial Profile Data


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Modeling Output:

Gas Flow Animation
http://localhost/var/www/apps/conversion/tmp/scratch_1/Georgetown_air.iv


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Modeling Output:

Solid Fuel Flow Animation
http://localhost/var/www/apps/conversion/tmp/scratch_1/Georgetown_fuel.iv


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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 kilnperformance

Improve waste gas incineration


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Advantages of Kiln Modeling

Model provides comprehensive informationthroughout 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 decisionsregarding kiln retrofits/replacements

Assists in optimizing burner and kiln

designs


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Modeling Application:

Burning Different Fuels

Heavy Oil

Petroleum Coke

Natural Gas


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Oil/Gas Burner Design


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Coal Burner Design NOx Emission

R1 R2

R3

Swirl Air

20 vanes

groove width = 17.7 mm

slot width =18.8 mm;

20 degrees

R0

R4

R5

R6

Coal

Transport Air

Axial Air

24 holes

18 mm Dia

R1

axial air

24 slots

0.0245 (1") wide0.0130 (0.51") deep

21 degrees inward

R2

R4

R3

R5

R0

Swirl air

No swirl

Transport air


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Direct Indirect Coal Combustion

Axial Air

Coal Air

Axial Air

Coal Air

Swirl Air

Swirl Air

Coal Air

Coal Air


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Burner with Different Primary Air

Oil Flame

@ Primary Air

Ratio of 22%

Oil Flame

@ Primary Air

Ratio of 60%


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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]


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Kiln Modeling Inputs: Overview

Site Survey andMeasurements

Mass and Energy Balance

Calculation

Kiln Geometry

Refractory Lining

Burner Design

Lime Feed Properties

Air Supplies

DCS Data Analysis


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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


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Example of Mass Balance

Mass In = Mass Out


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Example of Energy Balance

Energy In = Energy Out


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Kiln Geometry - Fire End

10' 6" Dia.

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

Burner

4' 23/4"

24"24"

9"

5' 6"

2' 9"

173/4"

kiln cL

Z

X

Barrel Start

(non rotated)


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Kiln Geometry - Front View

Hooddimension, kiln

diameter and

length, tilt

angle, kilnrotation

Location and

size of any

openings

Location and

tilt angle of

burner

15"

5' 3"

6' 7"

7' 3"

61/2"

41/2"

23/4"

2' 43/4"

15"

24" 12"

dia=?

24"

24"

2'7/8"

15o

20" Dia.

X


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Kiln Burner Design


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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

'

0.6

096

9.5

'

2.8

956

19.5

'

5.9

436m

39.5

'

12.0

39

84.5

'

25.7

556

134.5

'

40.9

956m

216'

65.8

368m

221'

67.3

608m

226.5

'

69.0

372m

Burner

3'

0.9144m

6"

0.1524m

18"

0.4572m

39"

0.9906m

102"

2.5

908

10'

3.0

48m

6'7"

2.0

066

97"

2.4

638

102"

2.5

908

108"

2.7

432m

54'

16.4592m

Chain

System

101"

2.5

654

01

2

2

3

3

4

4

4

0

aTaTaTaTaTaj

j

j

thermal conductivity, W/mk

T temperature, K

Material4a 3a 2a 1a 0a

Greenlite -2.554e-7 7.878e-4 5.248e-2

Refratherm 150 -3.571e-7 8.021e-4 0.1576

Magnel RSV 2.394e-12 -1.332e-8 2.771e-5 -0.02586 12.54

Kruzite - 70 5.908e-7 -0.0013 2.301

Clipper DP -3.571e-7 8.021e-4 0.1576


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Kiln Lime Mud


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Kiln DCS Data Display


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Kiln Operational Data Analyzer


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Selected Data Windows - 1


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Selected Data Windows - 2



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Computed Secondary Air Area



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Averaged Mill DCS Data

Parameter Case 19/25/2003 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) 6.14Dust 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



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Operation Conditions - Lime Fuel

Production rate 274.42 tpd 3.1761 kg/s

Total feed rate 663.12 tpd 7.6750 kg/sSolids content 80% 80%

CaCO3 462.23 tpd 5.3498 kg/s

Dust 57.29 tpd 0.6631 kg/s

Inerts 10.98 tpd 0.1270 kg/s

Moisture 132.62 tpd 1.54 kg/s

663.12 tpd 7.6750 kg/s

Oil flow rate 0.4440 kg/s

Oil 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/kgOil

Stoichiometric air for oil combustion 5.3359 kg/s

Atomizing steam flow rate lb/hr 0.08 kg/s

Mixture flow rate 0.5240

Mass fraction of oil in mixture 0.8473

Total heat input 19.8 MW

LIME

FUEL



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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 K

Primary air density 1.1835 kg/m^3

Primary Axial Air 25.0% 0.3200 kg/s

Primary Spin Air 75.0% 0.9600 kg/s

SECONDARY AIR

Secondary air temperature 298.15 K

Secondary air density 1.1835 kg/m^3

Left side flow area 0.2027 m*m

Right 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/s

Right side flow velocity 13.0334 m/s

Left side flow rate 0.1563 kg/s

Right side flow rate 0.1563 kg/s

BURNER/HOOD GAP AIR

Burner/Hood gap air temperature 298.15 K

Burner/Hood gap air density 1.1835 kg/m^3

Burner/Hood gap area 0.0488 m*m

Burner/Hood gap open area ratio 80.00%Burner/Hood gap velocity 13.0334 m/s

Burner/Hood flow rate 0.6018 kg/s

DISCHARGE GRATE AIR

Discharge grate air temperature 450 K

Discharge grate air density 0.7841 kg/m^3

Discharge grate area 0.5226 m*m

Discharge grate open area ratio 54.80%

Discharge grate velocity 16.0120 m/s

Discharge grate flow rate 3.5956 kg/s

Total air flow rate 5.7901 kg/s

Total air flow rate - stochiometric air flow rate 0.0001 kg/s

Air



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Flue Gas Calculation

speciesMolecular

Weight

Volume % 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 287.15

Ambient Pressure 101325 Pa

Ambient Temperature 298.15 K

Loss Coefficient 0.9

Firing End Draft -124.1 Pa

kg/s to tpd (metric) 86.4

28 16 44

1 CO + 0.5*O2 = CO2

16 64 44 36

2 CH4 + 2*O2 = CO2 + 2*H2O2 16 18

3 H2 + 0.5*O2 = H2O

12 32 44

4 C + O2 = CO2

100 44 56

5 CaCO3 = CO2 + CaO

14 16 30

6 N + 0.5*O2 = NO

32 32 64

7 S + O2 SO2

Species Reactions (with molecular weights)

limekiln modeling.ppt

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