© 2011 ANSYS, Inc. April 10, 20231
Thermal Oxidizer Modeling Using Combustion CFD Analysis
Jagadeesh UnnamCAMERON Process SystemsTechnology Center
© 2011 ANSYS, Inc. April 10, 20232
Agenda
• Introduction to CAMERON Thermal Oxidizer
• Motivation for CFD Simulation
• Modeling process
• Parameter variations
• Results used towards product development
© 2011 ANSYS, Inc. April 10, 20233
• Emission control device– Designed for > 99.9 % DRE
(Destruction Removal Efficiency)
• Primary applications: – Glycol dehydration off gases
• Other applications:– Tank vapors, Amine unit off gases,
Casing gases
• Non-assisted, natural draft combustion chamber
• Designed to provide the three essential T’s
– Temperature– Time– Turbulence
CAMERON Thermal Oxidizer(SHV Combustor)
Inline Arrestor
Air Damper (secondary & Tertiary)
Liquid Drip Pot
Fuel gas
Air Inlet (Flame Arrestor)
Burner Nozzle
Shield
Chamber
Pilot
Eductor
Sample Ports
To blowcase
Waste gas from SHE
© 2011 ANSYS, Inc. April 10, 20234
• Verification of theoretical assumptions and test data
• Observation of performance– Temperature profile• Combustion zone• Wall
– Hydrocarbon concentrations– Flow dynamics of air inlet & exhaust flue gases
• Optimization of combustion air flow
• Air dampener adjustments
• Chamber size reduction
• Chamber wall Insulation
Motivation for CFD Simulation
© 2011 ANSYS, Inc. April 10, 20235
• Sizing basis from existing filed operated unit
– 66” x 30’ external chamber– SA 516-70 (Material)
– 32” x 12’ Internal shield– 309 SS (Material)
• CAMERON SHV® Eductor & Burner Design
• Adjustable air inlets– Primary– Secondary– Tertiary
• Flame Arrestors
Geometric Details
© 2011 ANSYS, Inc. April 10, 20236
• Simulation case based on field operating unit
• Gas Properties:– Flow rate : 2.6 lb/min (constant)– Gas Inlet Temp : 275 F– Gas velocity out of the nozzle: 30 fps
• Assumptions – Constant gas flow inlet– Gas as 100% methane– Ambient atmosphere – Constant convective heat transfer
Flow Conditions and Fluid Properties
© 2011 ANSYS, Inc. April 10, 20237
Solver Settings
• 2D axis symmetric, Steady Sate
Models used
• Standard k- model
• Discrete Ordinates (DO) Radiation Model
• Eddy-Dissipation model
Mesh Size
• 143,232
Modeling Details
© 2011 ANSYS, Inc. April 10, 20238
• Temperature
• Velocity
• Flow vectors
• Hydrocarbon concentration
• Air dampener opening
• Wall temperature profiles
• Effects of external chamber size reduction
Type of Analysis & Optimization
© 2011 ANSYS, Inc. April 10, 20239
Cases Studied - Variations in air dampener setting
(lb/m
in)
% S
toic
.
(lb/m
in)
% S
toic
.
(lb/m
in)
% S
toic
.
Shei
ld
Cham
ber
Shei
ld
Cham
ber
ppm
1. with FA (Sec. 50%, Ter 50%) 5 17% 91 282% 92 284% 3100 1600 810 499 22. with FA (Sec. 50%, Ter 25%) 5 17% 99 305% 80 248% 3100 1600 792 506 23. with FA (Sec. 50%, Ter 12.5%) 6 17% 106 327% 62 192% 3100 1600 764 525 24. with FA (Sec. 50%, Ter 6.25%) 6 17% 114 351% 42 129% 3100 1600 749 550 35. FA Closed 4 12% 17 53% 18 55% 700 2000 580 1062 2361
Avg. CH4
Mass Pri. Air Sec. Air Ter. Air
Estimated Peak Temp. (F)
Peak wall temp. (F)
Cases (w.r.t FA - Flame Arrestors orientation)
Flow Rate
Note: Due to orientation of the dampener plates, 50% open equals the maximum achievable opening
© 2011 ANSYS, Inc. April 10, 202310
Chamber Temperature Profile – Variations in air dampener setting
Case 1: Sec. – 50% Ter. – 50%
Case 2: Sec. – 50% Ter. – 25%
Case 3: Sec. – 50% Ter. – 12.5%
Case 4: Sec. – 50% Ter. – 6.3%
Case 5 : FA’s ClosedCase 5: Sec. – 50% Ter. – 50%
© 2011 ANSYS, Inc. April 10, 202311
Wall Temperature Profile – Variations in air dampener setting
© 2011 ANSYS, Inc. April 10, 202312
• As reduced air damper setting resulted in acceptable performance, a new sizing basis was simulated for confirmation
• Reduced external chamber: 52”x 30’
• 21% reduction in diameter
• Adjustment to air inlet orientation
Chamber Size Reduction
Inline Arrestor
Air Damper (secondary & Tertiary)
Liquid Drip Pot
Fuel gas
Air Inlet (Flame Arrestor)
Burner Nozzle
Shield
Chamber
Pilot
Eductor
Sample Ports
To blowcase
Waste gas from SHE
52”
30”
30’
© 2011 ANSYS, Inc. April 10, 202313
Chamber Size Reduction
0 5 10 15 20 25 300
100200300400500600700800900
1000
Reduced Chamber Dia. (Non-Insulated)
Chamber Wall
Sheild Wall
Height, ft
Wal
l Tem
p., F
© 2011 ANSYS, Inc. April 10, 202314
Temperature Contours
Chamber Size Reduction - Performance
Velocity Contours Velocity Vectors
© 2011 ANSYS, Inc. April 10, 202315
Chamber Size Reduction - Performance
6. Uninsulated Outer Chamber 6 19% 140 431% 173 533% 3100 1600 755 515 27. Insulated Outer Chamber 6 20% 142 438% 181 558% 3100 1600 889 884 2
Reduced Chamber Cases (with FA's Sec. 50%, Ter. 50%)
(lb/m
in)
% S
toic
.
(lb/m
in)
% S
toic
.
(lb/m
in)
% S
toic
.
Shei
ld
Cham
ber
Shei
ld
Cham
ber
ppm
1. with FA (Sec. 50%, Ter 50%) 5 17% 91 282% 92 284% 3100 1600 810 499 22. with FA (Sec. 50%, Ter 25%) 5 17% 99 305% 80 248% 3100 1600 792 506 23. with FA (Sec. 50%, Ter 12.5%) 6 17% 106 327% 62 192% 3100 1600 764 525 24. with FA (Sec. 50%, Ter 6.25%) 6 17% 114 351% 42 129% 3100 1600 749 550 35. FA Closed 4 12% 17 53% 18 55% 700 2000 580 1062 2361
Avg. CH4
Mass Pri. Air Sec. Air Ter. Air
Estimated Peak Temp. (F)
Peak wall temp. (F)
Cases (w.r.t FA - Flame Arrestors orientation)
Flow Rate
© 2011 ANSYS, Inc. April 10, 202316
Chamber Size Reduction - Performance
Hydrocarbon Contours
• Verification of the three T’s
• Velocity vectors enable to optimize air inlets & avoid recirculation
• High combustion efficiency
0-100% 0-5%
© 2011 ANSYS, Inc. April 10, 202317
Chamber Wall – Non-Insulated vs. Insulated
0 5 10 15 20 25 300
100
200
300
400
500
600
700
800
900
1000
Chamber Wall Temperature (Insulated & Non-Insulated)
Non-Insulated InsulatedHeight, ft
Wal
l Tem
p., F
Non-Insulated Insulated
© 2011 ANSYS, Inc. April 10, 202318
6. Uninsulated Outer Chamber 6 19% 140 431% 173 533% 3100 1600 755 515 27. Insulated Outer Chamber 6 20% 142 438% 181 558% 3100 1600 889 884 2
Reduced Chamber Cases (with FA's Sec. 50%, Ter. 50%)
(lb/m
in)
% S
toic
.
(lb/m
in)
% S
toic
.
(lb/m
in)
% S
toic
.
Shei
ld
Cham
ber
Shei
ld
Cham
ber
ppm
1. with FA (Sec. 50%, Ter 50%) 5 17% 91 282% 92 284% 3100 1600 810 499 22. with FA (Sec. 50%, Ter 25%) 5 17% 99 305% 80 248% 3100 1600 792 506 23. with FA (Sec. 50%, Ter 12.5%) 6 17% 106 327% 62 192% 3100 1600 764 525 24. with FA (Sec. 50%, Ter 6.25%) 6 17% 114 351% 42 129% 3100 1600 749 550 35. FA Closed 4 12% 17 53% 18 55% 700 2000 580 1062 2361
Avg. CH4
Mass Pri. Air Sec. Air Ter. Air
Estimated Peak Temp. (F)
Peak wall temp. (F)
Cases (w.r.t FA - Flame Arrestors orientation)
Flow Rate
Chamber Wall – Non-Insulated vs. Insulated
© 2011 ANSYS, Inc. April 10, 202319
• Able to study performance & system limitations
• Incorporated both flow & combustion models
• Results in accordance with filed data
• Size reduction to standard models
• Wall insulation effects
Conclusions
© 2011 ANSYS, Inc. April 10, 202320
Questions ?
© 2011 ANSYS, Inc. April 10, 202321
Modeling process – Boundary ConditionsAppendix - 1
© 2011 ANSYS, Inc. April 10, 202322
Appendix - 2
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