optimization of heat transfer zones in distillation columns n.
Download
Skip this Video
Loading SlideShow in 5 Seconds..
OPTIMIZATION OF HEAT TRANSFER ZONES IN DISTILLATION COLUMNS PowerPoint Presentation
Download Presentation
OPTIMIZATION OF HEAT TRANSFER ZONES IN DISTILLATION COLUMNS

Loading in 2 Seconds...

play fullscreen
1 / 38

OPTIMIZATION OF HEAT TRANSFER ZONES IN DISTILLATION COLUMNS - PowerPoint PPT Presentation


  • 99 Views
  • Uploaded on

OPTIMIZATION OF HEAT TRANSFER ZONES IN DISTILLATION COLUMNS. X International PHOENICS Users Conference Melbourne, May 2004. Chemtech Solutions. AUTHORS. Chemtech - A Siemens Company, Rio de Janeiro / RJ – Brazil Petrobras / CENPES, Rio de Janeiro / RJ – Brazil. Bruno de Almeida Barbabela

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about 'OPTIMIZATION OF HEAT TRANSFER ZONES IN DISTILLATION COLUMNS' - zona


An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
optimization of heat transfer zones in distillation columns

OPTIMIZATION OF HEAT TRANSFER ZONES IN DISTILLATION COLUMNS

X International PHOENICS Users Conference

Melbourne, May 2004

authors
AUTHORS

Chemtech - A Siemens Company, Rio de Janeiro / RJ – Brazil

Petrobras / CENPES, Rio de Janeiro / RJ – Brazil

Bruno de Almeida Barbabela

Flávio Martins de Queiroz Guimarães

Silvia Waintraub

Glaucia Torres

introduction
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.
general settings
GENERAL SETTINGS
  • PHOENICS VERSION: 3.4
  • MULTI-PHASE MODEL: IPSA FULL
  • INTERPHASE PROPERTIES: By GROUND Coding.
    • Customization based on PETROX (Petrobras’ Process Simulation Tool) routines for calculation of petroleum fractionsproperties;
  • SPRAY FORMATION MODEL: By GROUND Coding.
    • Spray formation sources based on nozzle characteristics;
simulation strategy
SIMULATION STRATEGY

VALIDATION PHASE

Two-dimensional model (simplified)

Three-dimensional model

OPTIMIZATION PHASE

Two-dimensional model (simplified)

TUNNING PHASE

Three-dimensional model

analysis the chimneys
ANALYSIS – THE CHIMNEYS

VELOCITY ISO-SURFASE

constraints
CONSTRAINTS
  • 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.
energy transfer
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:

Heat Transfer Coefficient (h)

Nusselt Number

mass transfer
MASS TRANSFER

The mass transfer follows the model below and was based on the petroleum fractions properties calculated by the PETROX routines:

Molar Flux (Ni)

Mass Transf. Coef.

atomization droplet size
ATOMIZATION DROPLET SIZE

Sauter Diameter (D32)

The Sauter diameter is employed in atomization efficiency studies where mass transfer and chemical reactions are presented.

Correlations for the Sauter diameter are presented at Mugele [10] and Lefebvre [12].

validation conclusions
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.
slide28

Height (m)

Capacity factor (Cs)

RESULTS – SPRAY STABILITY

Heat Transfer Height vs. Cs

slide29

Dragged Liquid (%)

Droplet diameter (micron)

RESULTS – DROPLET SIZE

Dragged Liquid vs. Droplet Size

slide30

WIDE RANGE NOZZLE (90o CONE)

RESULTS – CS = 0.14ft/s

Temperature

Velocity

slide31

WIDE RANGE NOZZLE (90o CONE)

RESULTS – CS = 0.325ft/s

Temperature

Velocity

slide32

TWO SETS OF NOZZLES (90o CONE)

RESULTS – CS = 0.14ft/s

Temperature

Velocity

slide33

TWO SETS OF NOZZLES (90o CONE)

RESULTS – CS = 0.325ft/s

Temperature

Velocity

slide34

TWO SETS OF NOZZLES (90o CONE)

RESULTS – CS = 0.40ft/s

Temperature

Velocity

slide35

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.
slide36

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.
slide37

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.
slide38

Your Success is Our Goal

THANK YOU

Contact:

Flávio Guimarães

Senior Manager

Tel:+55 (21) 3233-5100

Mail:flavio.guimaraes@chemtech.com.br

Kontaktadresse:

Peter Muster

I&S GC

Schuhstraße 60

91052 Erlangen

Tel:09131-7-24607Mail:peter.muster@siemens.com

www.siemens.com/itps1 www.chemtech.com.br