www.psl.bc.ca recovery boiler modeling process simulation ltd
TRANSCRIPT
www.psl.bc.ca
Recovery BoilerModeling
Process Simulation Ltd.
www.psl.bc.ca
• 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
www.psl.bc.ca
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
www.psl.bc.ca
Mathematical Modeling Applications in Other Industries
Computer
Jet engines Weather
AutomotiveHarrier jet
www.psl.bc.ca
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
www.psl.bc.ca
Client List
• Weyerhaeuser USA• Weyerhaeuser Canada• Canfor• Kvaerner• Scott Paper• Anthony Ross• Weldwood
www.psl.bc.ca
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
www.psl.bc.ca
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
www.psl.bc.ca
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
www.psl.bc.ca
Input Data Required
• Boiler geometry
• Bed shape
• Convective section layout
• Air temperature and flow rate at each port
• Liquor characteristics
www.psl.bc.ca
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
www.psl.bc.ca
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
www.psl.bc.ca
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
www.psl.bc.ca
Tertiary Air Ports (20%)
Secondary Air Ports (30%)
Primary Air Ports (50%)
Base Case Modified Air System
Test Case Geometries
www.psl.bc.ca
Secondary Air System Problem and Solution
Jets collide
Carryover
Core forms
Secondaryjets
Liquor guns
Jets Interlace
Uniform flow
Secondaryjets
Base Case Modified Air System
www.psl.bc.ca
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
www.psl.bc.ca
1600150014001300120011001000900800700600
T[K]
Base Case
1600150014001300120011001000900800700600
T[K]
Modified Air System
Temperature Profiles
www.psl.bc.ca
Velocity Profiles
1614121086420
-2-4
20m/s
UpwardvelocityW [m/s]
Base Case
1614121086420
-2-4
20m/s
UpwardvelocityW [m/s]
Modified Air System
www.psl.bc.ca
X
Y
Z
X
Y
Z
---- drying---- pyrolysis
---- char
---- smelt
Fuel Particle Trajectories
Base Case Modified Air System
www.psl.bc.ca
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
www.psl.bc.ca
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)
www.psl.bc.ca
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
www.psl.bc.ca
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
www.psl.bc.ca
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