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Transcript of Www.psl.bc.ca Recovery Boiler Modeling Process Simulation Ltd.
![Page 1: Www.psl.bc.ca Recovery Boiler Modeling Process Simulation Ltd.](https://reader035.fdocuments.us/reader035/viewer/2022062219/551992f155034643068b46d2/html5/thumbnails/1.jpg)
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Recovery BoilerModeling
Process Simulation Ltd.
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• Develop modeling tools to improve existing designs and operating procedures, and to lower carry over and environmental impact
• Analyse performance of different air systems and liquor firing strategies
Objectives
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Introduction
• Process and equipment design was, until recently, based on experience
• Advances in numerical methods and computer speed and memory
– increased possibility of using more scientific methods, called mathematical modeling, for process design and optimization
Computing Hardware Trends
0.1
1
10
100
1000
10000
1980 1985 1990 1995 2000
Memory(MB)
0.1
1
10
100
1000
Speed(MIPS)
Memory
Speed
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Mathematical Modeling Applications in Other Industries
Computer
Jet engines Weather
AutomotiveHarrier jet
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Equipment Modeling Capabilities:
MatureDevelopingPreliminary
Time Time
Bark Boiler
BFB Bark Boiler
Hydrocyclone
Head boxDigester
Lime kiln
Gasifier
Recovery Boiler
We have active projects on this equipment
>306411
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Client List
• Weyerhaeuser USA• Weyerhaeuser Canada• Canfor• Kvaerner• Scott Paper• Anthony Ross• Weldwood
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Why Use Modeling?
• Recovery Boiler environment is too severe for measurement
• The model provides comprehensive information throughout the entire boiler at relatively low cost
• Can evaluate “what if” scenarios to improve operation/design
• Supplements steam chief and operator knowledge of recovery boiler operations
• Assists mill managers in making informed decisions regarding boiler refits/replacements
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Details of the Recovery Boiler Model
Liquor Combustion Model
• Advanced and verified solution algorithm
• Black liquor combustion modelDryingPyrolysis CO, CO2, CH4, H2, H2OChar gasification
• Gas phase combustion model
• Advanced radiation model
• Convective section model
• Char bed model
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Issues Addressed by the Model
• High excess air
• CO, CO2, and other emissions
• Mechanical carryover & plugging
• Bed blackouts
• Superheater and waterwall tube thermal stress failures
• Boiler stability and capacity
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Input Data Required
• Boiler geometry
• Bed shape
• Convective section layout
• Air temperature and flow rate at each port
• Liquor characteristics
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Model Predictions
• Gas species (e.g.
H2,O2,N2,CO,CO2,H2O,CH4)
distributions
• Gas flow velocity fields
• Temperature distributions and heat transfer to wall surfaces
• Liquor spray combustion and droplet trajectories.
• Carryover characteristics
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Model Validation
• Water Model Measurements• Full Scale Measurements
Isothermal flow validation
Hot flow validation• Temperature measurements at bullnose• Carryover prediction trends• CO emission trends• Velocity measurements
CE Boiler Model
B&W Boiler Model
Different aspects of model results have been validated against data from operating boilers
Different aspects of model results have been validated against data from operating boilers
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Recovery Boiler Refit Example
• High plugging rates
• High gas temperature at superheater
• Bed growth control
The Issue:
The Objective:
• To recommend modifications to air system
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Tertiary Air Ports (20%)
Secondary Air Ports (30%)
Primary Air Ports (50%)
Base Case Modified Air System
Test Case Geometries
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Secondary Air System Problem and Solution
Jets collide
Carryover
Core forms
Secondaryjets
Liquor guns
Jets Interlace
Uniform flow
Secondaryjets
Base Case Modified Air System
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PrimaryV = 30 m/s
50% Air T = 423 K
M = 46 kg/sz = 1.2 m
Liquor Guns
HV=15000 kJ/kgT = 400 K
M = 18 kg/sz = 7 m
BaseCase
SecondaryV = 85 m/s
30% Air T = 423 K
M = 27.6 kg/sz = 3 m
Tertiary20% Air
V = 50 m/sT = 423 K
M = 18.4 kg/sz = 10 m
ModifiedAir
SystemTertiary20% Air
V = 50 m/sT = 423 K
M = 18.4 kg/sz = 10 m
SecondaryV = 85 m/s
30% Air T = 423 K
M = 27.6 kg/sz = 3 m
CommonAir/LiquorSystem Data in
Plan View
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1600150014001300120011001000900800700600
T[K]
Base Case
1600150014001300120011001000900800700600
T[K]
Modified Air System
Temperature Profiles
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Velocity Profiles
1614121086420
-2-4
20m/s
UpwardvelocityW [m/s]
Base Case
1614121086420
-2-4
20m/s
UpwardvelocityW [m/s]
Modified Air System
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X
Y
Z
X
Y
Z
---- drying---- pyrolysis
---- char
---- smelt
Fuel Particle Trajectories
Base Case Modified Air System
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Y
Z
X
2001601401201008060402050
Modified Air System
Total Carryoverat Superheater0.03%
Carryovermass flux[g/s/m
2]
Y
Z
X
2001601401201008060402050
Carryovermass flux[g/s/m
2]
Base Case
Total Carryoverat Superheater4.06%
Carryover Mass Flux
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02468
101214161820
Base Case
Modified Air System
Water SmeltPyro. Char
Wall
0
5
10
15
20
25
30
Water SmeltPyro. Char
InFlight
0
1
2
3
4
5
Water SmeltPyro. Char
Carryover
0
3
6
9
12
15
Water SmeltPyro. Char
Bed
Black Liquor Particulate Distribution(% of total liquor input)
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X
Y
Z
O20.160.140.120.10.080.070.060.050.040.02
X
Y
Z
O20.160.140.120.10.080.070.060.050.040.02
Oxygen Concentration Distribution
Base Case Modified Air System
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X
Y
Z
CO0.10.050.010.0050.0030.0010.00050.00015E-05
X
Y
Z
CO0.10.050.010.0050.0030.0010.00050.00015E-05
Carbon Monoxide Concentration Distribution
Base Case Modified Air System
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Conclusions
• The modified air system:
– Larger air ports provides better jet penetration.
– Increases gas mixing
– Breaks up the vertical air core
– Significantly reduces plugging rates.
– Reduces gas temperatures at superheater
• In general, modeling:
– Provides detailed data to facilitate efficient operation of Recovery Boilers.
– Helps mill managers make informed decisions regarding boiler refits/replacements