1 / 30

Master’s Dissertation Defense Carlos M. Teixeira Supervisors: Prof. José Carlos Lopes

Direct Numerical Simulation of Fixed-Bed Reactors: Effect of Random Packing. Master’s Dissertation Defense Carlos M. Teixeira Supervisors: Prof. José Carlos Lopes Eng. Matthieu Rolland. 17 th July 2013. Outline. Direct Numerical Simulation of Fixed-Bed Reactors: Effect of Random Packing.

tybalt
Télécharger la présentation

Master’s Dissertation Defense Carlos M. Teixeira Supervisors: Prof. José Carlos Lopes

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. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Direct Numerical Simulation of Fixed-Bed Reactors: Effect of Random Packing Master’s Dissertation Defense Carlos M. Teixeira Supervisors: Prof. José Carlos Lopes Eng. Matthieu Rolland 17th July 2013

  2. Outline Direct Numerical Simulation of Fixed-Bed Reactors: Effect of Random Packing • Introduction • Objectives • State of the Art • Methodology • Results and Discussion • Conclusions FEUP/IFPEN

  3. Introduction Direct Numerical Simulation of Fixed-Bed Reactors: Effect of Random Packing • Catalysts performance evaluation • Performed in unitsat pilot scale • The trend is to reduce the size of testing units(economic and safety reasons) • Catalyst size remains constant (customer demands) • Consequence Reactors with low tube-to-particle diameter ratio ) FEUP/IFPEN

  4. Introduction Direct Numerical Simulation of Fixed-Bed Reactors: Effect of Random Packing • Reactors with low tube-to-particle diameter ratio • Pseudo Homogeneous Models may not be valid • Local Phenomena are dominant • Wall Effect • Packing Effect FEUP/IFPEN

  5. Introduction Direct Numerical Simulation of Fixed-Bed Reactors: Effect of Random Packing Example of Packing Effect • Problem Description • Packing of eight cylinders with different arrangements • Fluid with zero concentration at the inlet flows through the packing • Laminar regime • Cylinders with constant concentration in their surface • Transfer solute to the fluid Normalized outlet concentration for the different arrangements FEUP/IFPEN

  6. Outline Direct Numerical Simulation of Fixed-Bed Reactors: Effect of Random Packing • Introduction • Objectives • State of the Art • Methodology • Results and Discussion • Conclusions FEUP/IFPEN

  7. Objectives Direct Numerical Simulation of Fixed-Bed Reactors: Effect of Random Packing • Study the phenomena of single phase fluid flow through fixed-bed reactors at low particle Reynolds number • Understand how the packing structure affects the flow FEUP/IFPEN

  8. Outline Direct Numerical Simulation of Fixed-Bed Reactors: Effect of Random Packing • Introduction • Objectives • State of the Art • Methodology • Results and Discussion • Conclusions FEUP/IFPEN

  9. State of the Art Direct Numerical Simulation of Fixed-Bed Reactors: Effect of Random Packing CFD Simulation of Fixed-Bed Reactors • Benchmark Method: Lattice Boltzmann • Finite Volume method has been successfully used by many authors • In most published works, the ratio of tube-to-particle diameter is low FEUP/IFPEN

  10. State of the Art Direct Numerical Simulation of Fixed-Bed Reactors: Effect of Random Packing CFD Simulation of Fixed-Bed Reactors • Coupling between Hydrodynamics, Heat Transfer and Chemical Reaction: • Less works on the literature • Applied in small size problems (dozens of particles) • Particle shape: mostly spheres FEUP/IFPEN

  11. Outline Direct Numerical Simulation of Fixed-Bed Reactors: Effect of Random Packing • Introduction • Objectives • State of the Art • Methodology • Results and Discussion • Conclusions FEUP/IFPEN

  12. Methodology Direct Numerical Simulation of Fixed-Bed Reactors: Effect of Random Packing Coupling between DEM and CFD • GRAINS3D (Packing Simulation) • PeliGRIFF (Fluid Flow Simulation) FEUP/IFPEN

  13. Methodology Direct Numerical Simulation of Fixed-Bed Reactors: Effect of Random Packing Grid Refinement Studies Relative error in the inlet velocity as a function of the grid resolution (ε=0.799, l/dp=1) FEUP/IFPEN

  14. Outline Direct Numerical Simulation of Fixed-Bed Reactors: Effect of Random Packing • Introduction • Objectives • State of the Art • Methodology • Results and Discussion • Conclusions FEUP/IFPEN

  15. Results and Discussion Direct Numerical Simulation of Fixed-Bed Reactors: Effect of Random Packing Flow through Structured Packed Beds • Unit cell approach (a) (b) A packed bed of simple cubic arrangement of spheres. a) Unit cell b) Alternative representation of a simple cubic unit cell. FEUP/IFPEN

  16. Results and Discussion Direct Numerical Simulation of Fixed-Bed Reactors: Effect of Random Packing Flow through Structured Packed Beds of Spheres • Validation Case Comparison between the simulated dimensionless pressure drop and results from Hill et al. (2001) for a dilute array of spheres (ε=0.799) FEUP/IFPEN

  17. Results and Discussion Direct Numerical Simulation of Fixed-Bed Reactors: Effect of Random Packing Flow through Structured Packed Beds of Cylinders • Effect of cylinder orientation Effect of cylinders orientation on dimensionless pressure drop (ε=0.799, l/dp=1) FEUP/IFPEN

  18. Results and Discussion Direct Numerical Simulation of Fixed-Bed Reactors: Effect of Random Packing Flow through Structured Packed Beds of Cylinders • Transition from laminar regime to unsteady and chaotic flow Particle Reynolds number as a function of time for 45º orientation (ΔP=10 Pa) FEUP/IFPEN

  19. Results and Discussion Direct Numerical Simulation of Fixed-Bed Reactors: Effect of Random Packing Flow through Randomly Packed Beds of Cylinders Case ID FBR1 FBR2 FBR3 Nº of particles 540 200 100 Porosity, ε 0.451 0.444 0.467 FEUP/IFPEN

  20. Results and Discussion Direct Numerical Simulation of Fixed-Bed Reactors: Effect of Random Packing Flow through Randomly Packed Beds of Cylinders • Simulated Packed Beds Grid parameters and computing times on 128 processors FEUP/IFPEN

  21. Results and Discussion Direct Numerical Simulation of Fixed-Bed Reactors: Effect of Random Packing Flow through Randomly Packed Beds of Cylinders • Pressure Drop Dimensionless pressure drop as a function of porosity. Comparison between simulations and Ergun correlation predictions (Redp=1). FEUP/IFPEN

  22. Results and Discussion Direct Numerical Simulation of Fixed-Bed Reactors: Effect of Random Packing Flow through Randomly Packed Beds of Cylinders • Spatial Velocity Distribution • Three different zones are identified: • Recirculation zones in the packing top and bottom and in the wake of the particles (with negative velocities) • High velocity zones where the void fraction is small and the velocity increases up to a factor of 15 • Low velocity zones near the particles surfaces FEUP/IFPEN

  23. Results and Discussion Direct Numerical Simulation of Fixed-Bed Reactors: Effect of Random Packing Flow through Randomly Packed Beds of Cylinders • Statistical Velocity Distribution Probability density functions of normalized z-velocity in different zones of the fixed-bed. FEUP/IFPEN

  24. Results and Discussion Direct Numerical Simulation of Fixed-Bed Reactors: Effect of Random Packing Flow through Randomly Packed Beds of Cylinders • Statistical Velocity Distribution (link with porosity) Inlet Outlet Axial average porosity profile FEUP/IFPEN

  25. Results and Discussion Direct Numerical Simulation of Fixed-Bed Reactors: Effect of Random Packing Flow through Randomly Packed Beds of Cylinders • Statistical Velocity Distribution (link with porosity) Probability density functions of normalized z-velocity for different porosities FEUP/IFPEN

  26. Results and Discussion Direct Numerical Simulation of Fixed-Bed Reactors: Effect of Random Packing Flow through Randomly Packed Beds of Cylinders • Statistical Velocity Distribution Probability density functions of normalized x-velocity for different porosities FEUP/IFPEN

  27. Outline Direct Numerical Simulation of Fixed-Bed Reactors: Effect of Random Packing • Introduction • Objectives • State of the Art • Methodology • Results and Discussion • Conclusions FEUP/IFPEN

  28. Conclusions Direct Numerical Simulation of Fixed-Bed Reactors: Effect of Random Packing Flow through Structured Packed Beds • The methodology was validated with well-established cases from the literature • Dependence of Pressure Drop across Packed Beds of cylinders on its orientation was studied • Transition from steady laminar flow to time oscillatory and chaotic flow was observed at FEUP/IFPEN

  29. Conclusions Direct Numerical Simulation of Fixed-Bed Reactors: Effect of Random Packing Flow through Randomly Packed Beds • Good agreement between Ergun’s pressure drop predictions and simulation results were found • Velocity distributions were analyzed and three different zones were identified • Velocity distributions appear to follow the average local porosity: the length to establish the flow is identical to the length to establish the porosity FEUP/IFPEN

  30. www.ifpenergiesnouvelles.com Direct Numerical Simulation of Fixed-Bed Reactors: Effect of Random Packing Thank you for your attention FEUP/IFPEN

More Related