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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Modeling Application:
Oil/Gas Burner Design
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Modeling Application:
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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Modeling Application:
Direct Indirect Coal Combustion
Axial Air
Coal Air
Axial Air
Coal Air
Swirl Air
Swirl Air
Coal Air
Coal Air
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Modeling Application:
Burner with Different Primary Air
Oil Flame
@ Primary Air
Ratio of 22%
Oil Flame
@ Primary Air
Ratio of 60%
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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]
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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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Kiln Modeling Inputs:
Example of Mass Balance
Mass In = Mass Out
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Kiln Modeling Inputs:
Example of Energy Balance
Energy In = Energy Out
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Kiln Modeling Inputs:
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 Modeling Inputs:
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 Modeling Inputs:
Kiln Burner Design
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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
'
0.6
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 Modeling Inputs:
Kiln Lime Mud
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Kiln Modeling Inputs:
Kiln DCS Data Display
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Kiln Modeling Inputs:
Kiln Operational Data Analyzer
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Kiln Modeling Inputs:
Selected Data Windows - 1
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Kiln Modeling Inputs:
Selected Data Windows - 2
Kiln Modeling Inputs:
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Computed Secondary Air Area
Kiln Modeling Inputs:
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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
Kiln Modeling Inputs:
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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
Kiln Modeling Inputs:
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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
Kiln Modeling Inputs:
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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)