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Experimental Investigation and CFD Simulation of the Flow Pattern of the FCC's Fluidized Bed Regenerator

Azarnivand, Abbas | 2016

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 49230 (06)
  4. University: Sharif University of Technology
  5. Department: Chemical and Petroleum Engineering
  6. Advisor(s): Dehkordi, Asghar Molaei; Seifkordi, Aliakbar; Behjat, Yaghoub
  7. Abstract:
  8. Hydrodynamic behavior of gas-solid fluidization in large-diameter beds like FCC regenerator exhibits complex aspects. To investigate the gas-solid flow pattern of UOP's combustor-style FCC regenerator, a lab-scale regenerator was designed by a downscale factor of 0.045. The regenerator's operation and fluidization of FCC particles through it was examined and pressure axial distributions were measured and analyzed at different superficial air velocities. 3D CFD simulation of the regenerator was performed with Eulerian-Eulerian approach to investigate the effects of operating conditions, including superficial air velocity, catalyst mass flux, presence of recirculated catalyst, and the inequality of spent and recirculated catalyst and also the turbulent dispersion force in the modeling interphase interaction on the combustor-style regenerator flow pattern. As a result, various aspects of its hydrodynamic behavior, potentially effective in regeneration of catalyst, were examined. Based on simulations results, applying turbulent dispersion force by Simonin model, results in a different radial distribution in the lower part of the combustor and shows a greater deviation of the flow in the riser from plug flow. Combustor flow pattern shows different behavior at various sections because of asymmetric location of catalyst inlets and riser outlets. It is also shown that recirculated catalyst influences gas-solid flow pattern of combustor. In fact, simultaneous presence of spent and recirculated catalysts considerably reduces the air bypass and makes catalyst particles distribute over a wider range of the cross section. In the lower part of the combustor, vortexes exist at some sections. Vortexes improve the mixing of spent catalyst and recirculated catalyst and also the mixing of air and catalyst. Recirculated catalyst to spent catalyst ratio can be considered as a factor that determines the quality of spent and recirculated catalysts mixing because increasing this ratio to 1.5 changes the quality and the location of vortexes. Changing superficial air velocity in the range of 1-2m/s (based on the cross section of the combustor lower part) noticeably influences the flow pattern; while the flow pattern is less dependent on the catalyst mass flux variations in the range of 14.89-27.67kg/m2s (based on the cross section of the combustor lower part). The deviation of air while flowing in the combustor, predicted by the simulation is observed. Also, the simulated flow pattern around the disengager arms and about the outer terminal of the riser, can be verified by experimental observations
  9. Keywords:
  10. Flow Patterns ; Fluidized Bed ; Fluid Catalytic Cracking (FCC)Process ; Fluidized Bed Reactor ; Computational Fluid Dynamics (CFD) ; Combustor-Style Regenerator ; Gas-Solid Flow

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