Post on 28-Mar-2015
transcript
Your Success is Our Goalwww.siemens.com/itps1 www.chemtech.com.br
OPTIMIZATION OF HEAT TRANSFER ZONES IN DISTILLATION COLUMNS
X International PHOENICS Users Conference
Melbourne, May 2004
Your Success is Our Goal
Dis
tilla
tion_
2004
.ppt
S
lide
2©
IT
PS
200
4
Vacuum Towers
Chemtech Solutions
Your Success is Our Goal
Dis
tilla
tion_
2004
.ppt
S
lide
3©
IT
PS
200
4
Vacuum Towers
Chemtech - A Siemens Company, Rio de Janeiro / RJ – BrazilChemtech - A Siemens Company, Rio de Janeiro / RJ – Brazil
Petrobras / CENPES, Rio de Janeiro / RJ – BrazilPetrobras / CENPES, Rio de Janeiro / RJ – Brazil
Bruno de Almeida BarbabelaBruno de Almeida Barbabela
Flávio Martins de Queiroz GuimarãesFlávio Martins de Queiroz Guimarães
Silvia WaintraubSilvia Waintraub
Glaucia TorresGlaucia Torres
AUTHORS
Your Success is Our Goal
Dis
tilla
tion_
2004
.ppt
S
lide
4©
IT
PS
200
4
Vacuum Towers
INTRODUCTION
The use of empty spray sections (no packing) in heat transfer regions of vacuum towers allows a high deep cut operation, due to the reduction of the pressure drop along the column.
Simulation studies show that a reduction of 1 mmHg in pressure results in an increase of approximately 0.3% in the gas oils yield. This represents a profit of about US$ 13,000,000 per year for a typical unit with a feed rate of 30,000 m3/day. Other benefits are the decrease in investment and maintenance cost.
Petrobras has four vacuum towers in Rio de Janeiro’s refinery designed by Badger Limited in 1975 without any device in the top pump-around section. In the present work we will present the CFD model developed to analyze this kind of tower.
Your Success is Our Goal
Dis
tilla
tion_
2004
.ppt
S
lide
5©
IT
PS
200
4
Vacuum Towers
INTRODUCTION
Spray Nozzles
Chimneys
Your Success is Our Goal
Dis
tilla
tion_
2004
.ppt
S
lide
6©
IT
PS
200
4
Vacuum Towers
• PHOENICS VERSIONPHOENICS VERSION:: 3.4
• MULTI-PHASE MODELMULTI-PHASE MODEL:: IPSA FULL
• INTERPHASE PROPERTIESINTERPHASE PROPERTIES:: By GROUND Coding.
Customization based on PETROX (Petrobras’ Process Simulation Tool) routines for calculation of petroleum fractions properties;
• SPRAY FORMATION MODELSPRAY FORMATION MODEL:: By GROUND Coding.
Spray formation sources based on nozzle characteristics;
GENERAL SETTINGS
Your Success is Our Goal
Dis
tilla
tion_
2004
.ppt
S
lide
7©
IT
PS
200
4
Vacuum Towers
VALIDATION PHASE
OPTIMIZATION PHASE
TUNNING PHASE
Two-dimensional model (simplified)
Three-dimensional model
Two-dimensional model (simplified)
Three-dimensional model
SIMULATION STRATEGY
Your Success is Our Goal
Dis
tilla
tion_
2004
.ppt
S
lide
8©
IT
PS
200
4
Vacuum Towers
GEOMETRY – THE EMPTY SPRAY SECTION
Your Success is Our Goal
Dis
tilla
tion_
2004
.ppt
S
lide
9©
IT
PS
200
4
Vacuum Towers
GEOMETRY – THE SPRAY NOZZLES
Your Success is Our Goal
Dis
tilla
tion_
2004
.ppt
S
lide
10©
IT
PS
200
4
Vacuum Towers
GEOMETRY – THE CHIMNEYS
Your Success is Our Goal
Dis
tilla
tion_
2004
.ppt
S
lide
11©
IT
PS
200
4
Vacuum Towers
ANALYSIS – THE CHIMNEYS
VELOCITY ISO-SURFASE
Your Success is Our Goal
Dis
tilla
tion_
2004
.ppt
S
lide
12©
IT
PS
200
4
Vacuum Towers
• Spray generated droplets have a constant and uniform diameter (though it can change along the tower);
• No interaction between droplets;
• Since the droplets are very small, they behave as a film, without temperature gradient from the bulk of the droplet to the interface;
• The vapor phase has an ideal gas mixture behavior;
• Only the main petroleum fractions were considered for the properties calculation;
• Diffusive transport of the petroleum fractions into the same phase was not considered.
CONSTRAINTS
Your Success is Our Goal
Dis
tilla
tion_
2004
.ppt
S
lide
13©
IT
PS
200
4
Vacuum Towers
ENERGY TRANSFER
The heat transfer between phases is presented below (without convective and diffusive terms) and was based on the heat transfer of small spherical droplets in a continuous vapor phase:
LVp
jjj
jjj Ht
mTTAph
t
TCpV ...... int
Heat Transfer Coefficient (h)
p
D
D
kNuh
.
31
21
Pr.Re.6,00,2 DDNu Nusselt Number
Your Success is Our Goal
Dis
tilla
tion_
2004
.ppt
S
lide
14©
IT
PS
200
4
Vacuum Towers
MASS TRANSFER
The mass transfer follows the model below and was based on the petroleum fractions properties calculated by the PETROX routines:
ipip MANt
m..
,,.. iSipci CCAKN
Mass Transf. Coef.p
Dmic D
NuDK
.,
Molar Flux (Ni)
Your Success is Our Goal
Dis
tilla
tion_
2004
.ppt
S
lide
15©
IT
PS
200
4
Vacuum Towers
ATOMIZATION DROPLET SIZE
Sauter Diameter (D32)
...,,,32 pcpPfD o
Correlations for the Sauter diameter are presented at Mugele [10] and Lefebvre [12].
The Sauter diameter is employed in atomization efficiency studies where mass transfer and chemical reactions are presented.
Your Success is Our Goal
Dis
tilla
tion_
2004
.ppt
S
lide
16©
IT
PS
200
4
Vacuum Towers
Your Success is Our Goal
Dis
tilla
tion_
2004
.ppt
S
lide
17©
IT
PS
200
4
Vacuum Towers
VALIDATION
Temperature Profile (phase 5)
40
50
60
70
80
90
100
110
120
24900 25900 26900 27900 28900
Elevation (mm)
Tem
per
atu
re (
Cel
siu
s)
PHOENICS
Experimental
Your Success is Our Goal
Dis
tilla
tion_
2004
.ppt
S
lide
18©
IT
PS
200
4
Vacuum Towers
VALIDATION
Height of Heat Transfer Zone
0
500
1000
1500
2000
2500
3000
3500
0,60 0,80 1,00 1,20 1,40 1,60
Reflux (normalized)
He
igh
t (m
m)
PHOENICS
Exp.
Exp.
PHOENICS
Your Success is Our Goal
Dis
tilla
tion_
2004
.ppt
S
lide
19©
IT
PS
200
4
Vacuum Towers
VALIDATION
40
50
60
70
80
90
100
110
120
24900 25900 26900 27900 28900
Height above ground (mm)
Te
mp
era
ture
(C
els
ius
)
PHOENICS 2D
Field Data
PHOENICS 3D
Your Success is Our Goal
Dis
tilla
tion_
2004
.ppt
S
lide
20©
IT
PS
200
4
Vacuum Towers
VALIDATION – CONCLUSIONS
• The computational model fits well the experimental data for the 2D model, although it must be enhanced for the 3D model.
• No significant drag of the oil droplets was notified at the current operational conditions.
• From the analysis of the results, the current 60o spray cone seems to be not suitable. A wide range nozzle is recommended.
Your Success is Our Goal
Dis
tilla
tion_
2004
.ppt
S
lide
21©
IT
PS
200
4
Vacuum Towers
Your Success is Our Goal
Dis
tilla
tion_
2004
.ppt
S
lide
22©
IT
PS
200
4
Vacuum TowersCAPACITY FACTOR ANALYSISRESULTS – CS = 0.05 ft/s
Temperature Velocity
Your Success is Our Goal
Dis
tilla
tion_
2004
.ppt
S
lide
23©
IT
PS
200
4
Vacuum TowersCAPACITY FACTOR ANALYSISRESULTS – CS = 0.10 ft/s
Temperature Velocity
Your Success is Our Goal
Dis
tilla
tion_
2004
.ppt
S
lide
24©
IT
PS
200
4
Vacuum TowersCAPACITY FACTOR ANALYSISRESULTS – CS = 0.20 ft/s
Temperate Velocity
Your Success is Our Goal
Dis
tilla
tion_
2004
.ppt
S
lide
25©
IT
PS
200
4
Vacuum TowersCAPACITY FACTOR ANALYSISRESULTS – CS = 0.30 ft/s
Temperature Velocity
Your Success is Our Goal
Dis
tilla
tion_
2004
.ppt
S
lide
26©
IT
PS
200
4
Vacuum TowersCAPACITY FACTOR ANALYSISRESULTS – CS = 0.325 ft/s
Temperature Velocity
Your Success is Our Goal
Dis
tilla
tion_
2004
.ppt
S
lide
27©
IT
PS
200
4
Vacuum TowersCAPACITY FACTOR ANALYSISRESULTS – CS = 0.35 ft/s
Temperature Velocity
Your Success is Our Goal
Dis
tilla
tion_
2004
.ppt
S
lide
28©
IT
PS
200
4
Vacuum Towers
RESULTS – SPRAY STABILITY
Heat Transfer Height vs. CsHeat Transfer Height vs. Cs
0.00
1.00
2.00
3.00
4.00
5.00
6.00
7.00
0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4
Fator de Capacidade (CS)
Alt
ura
de
Tro
ca
Té
rmic
a (
m)
Capacity factor (Cs)
Hei
gh
t (m
)
Your Success is Our Goal
Dis
tilla
tion_
2004
.ppt
S
lide
29©
IT
PS
200
4
Vacuum Towers
RESULTS – DROPLET SIZE
Dragged Liquid vs. Droplet SizeDragged Liquid vs. Droplet Size
Droplet diameter (micron)
Dra
gg
ed L
iqu
id (
%)
Your Success is Our Goal
Dis
tilla
tion_
2004
.ppt
S
lide
30©
IT
PS
200
4
Vacuum TowersWIDE RANGE NOZZLE (90o CONE)RESULTS – CS = 0.14 ft/s
Temperature Velocity
Your Success is Our Goal
Dis
tilla
tion_
2004
.ppt
S
lide
31©
IT
PS
200
4
Vacuum TowersWIDE RANGE NOZZLE (90o CONE)RESULTS – CS = 0.325 ft/s
VelocityTemperature
Your Success is Our Goal
Dis
tilla
tion_
2004
.ppt
S
lide
32©
IT
PS
200
4
Vacuum TowersTWO SETS OF NOZZLES (90o CONE)RESULTS – CS = 0.14 ft/s
Temperature Velocity
Your Success is Our Goal
Dis
tilla
tion_
2004
.ppt
S
lide
33©
IT
PS
200
4
Vacuum TowersTWO SETS OF NOZZLES (90o CONE)RESULTS – CS = 0.325 ft/s
Temperature Velocity
Your Success is Our Goal
Dis
tilla
tion_
2004
.ppt
S
lide
34©
IT
PS
200
4
Vacuum TowersTWO SETS OF NOZZLES (90o CONE)RESULTS – CS = 0.40 ft/s
VelocityTemperature
Your Success is Our Goal
Dis
tilla
tion_
2004
.ppt
S
lide
35©
IT
PS
200
4
Vacuum Towers
CONCLUSIONS
• The maximum capacity factor allowed for spray cone stabilization simulated (between 0.325 and 0.375 ft/s) was similar to the values reported by experimental observations and experts opinions;
• Since the simulations showed that the effective height of the heat transfer zone has low dependence on the mean droplet size, it is recommended that the spray nozzles were adjusted to be biased toward the generation of greater droplets in order to minimize the liquid drag;
• The use of wider angles of sprays reduces the effective height of heat transfer zone despite the loss of spray stability;
• The use of two levels of distributors is recommended for improve the spray cones stability and reduce the effective height of the heat transfer zone.
Your Success is Our Goal
Dis
tilla
tion_
2004
.ppt
S
lide
36©
IT
PS
200
4
Vacuum Towers
CONCLUSIONS
• Although some improvements have to be made, CFD seems to be an useful tool to analyze the performance of heat transfer and spray formation in vacuum towers. The use of this technology on the optimization of current towers and on the project of new ones is recommended to improve their performance.
Your Success is Our Goal
Dis
tilla
tion_
2004
.ppt
S
lide
37©
IT
PS
200
4
Vacuum Towers
NEXT STEPS
• Petrobras will use the model to perform other studies:
• Variation of the liquid reflux temperature
• Variation of the height of the spray nozzles
• Calculation of the global heat transfer coefficient
• To enhance the model of the petroleum mixture, considering more fractions in it.
Your Success is Our Goal
Dis
tilla
tion_
2004
.ppt
S
lide
38©
IT
PS
200
4
Vacuum Towers
Kontaktadresse:
Peter MusterI&S GCSchuhstraße 6091052 ErlangenTel: 09131-7-24607
Mail: peter.muster@siemens.com
Your Success is Our Goal
www.siemens.com/itps1 www.chemtech.com.br
Contact:
Flávio GuimarãesSenior Manager
Tel: +55 (21) 3233-5100
Mail: flavio.guimaraes@chemtech.com.br
THANK YOU