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Journal Report

Journal Report. About CFD. Hongna Wang Nov. 28, 2012. Investigation of hydrodynamics, heat transfer and cracking reaction in a heavy oil riser with bottom airlift loop mixer Jian Chang , Fandong Meng Luoyang, SINOPEC Chemical Engineering Science 78 (2012) 128–143. Introduction.

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Journal Report

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  1. Journal Report About CFD Hongna Wang Nov. 28, 2012

  2. Investigation of hydrodynamics, heat transfer and cracking reaction in a heavy oil riser with bottom airlift loop mixer Jian Chang , Fandong Meng Luoyang, SINOPEC Chemical Engineering Science 78 (2012) 128–143

  3. Introduction • This paper aims at CFD investigation and optimization of hydrodynamics, heat transfer and cracking reaction in a heavy oil riser together with a bottom airlift loop mixer, which is operated with the new operating mode of low temperature contact and high catalyst-to-oil ratio. By extending a validated gas–solid two-phase flow model (Zheng et al., 2001) to incorporate the feedstock vaporization and a 12-lump heavy oil reaction kinetics model (Wu, 2009), a three-phase CFD model is estab- lished . [1] Wu, F.Y., 2009. Study on Lumped Kinetic Model for FDFCC. (Doctor Thesis). East China University of Science and Technology, China. [2] Zheng, Y.,Wan,X.,Qian,Z.,Wei,F.,Jin,Y.,2001.Numericalsimulationofthegas- particle turbulent flow in riser reactor based on k–e–kp–ep–y two-fluid model. Chem. Eng.Sci.56,6813–6822.

  4. Modelling • 12-lump kinetics model (Wu, 2009) is used to describe the cracking reaction of heavy oil in the current riser reactor. [1]Lan, X.Y., Xu, C.M., Wang, G., Wu, L., Gao, J.S., 2009. CFD mdeling of gas-particle flow and cracking reaction in two-stage riser FCC reactors. Chem. Eng. Sci. 64, 3847–3858. .

  5. Validation

  6. Hydrodynamics in riser • Drastically non-uniform in the axial and radial direction • Deteriorating the gas-solid contact and then the cracking reaction

  7. Heat transfer characteristics • Well mixed in mixer • Complex in the nozzle region

  8. Optimization of operating parameters • Injection angle----60°is superior

  9. Optimization of operating parameters • Reaction time --- a short time i.e. 3.02s is favorable.

  10. Optimization of operating parameters • Catalyst-to-oil ratio --- 7-8 is more suitable.

  11. Conclusions • Extending a validated gas–solid flow model and 12-lump kinetic model, a three-phase flow and reaction model is established. • The bottom airlift loop mixer causes the hot and the cool catalyst well mix and obtains a uniform catalyst temperature at riser inlet. • Preferable condition for a higher light liquid yield: injection angle of 60°; catalyst-to-oil ratio of 7-8; and a shorter reaction time of 3.02 s .

  12. Steady-state simulation of core-annulus flow in a circulating fluidized bed (CFB) riser Xi Gao, Li-Jun Wang Zhejiang University Chemical Engineering Science 78 (2012) 98–110

  13. Introduction • A steady-state multiphase CFD model is proposed for the simulation of core-annulus flow in a circulating fluidized bed (CFB) riser. • There is no demonstration in the literature that the unrealistic sensitivity of steady models is well settled. • The main objectives are: • (1) to develop a new steady-state model to simulate the core-annulus flow, which can eliminate the unrealistic sensitivity while consuming less computational resources compared with transient models; • (2) to conduct comparative analysis of the effects of inlet boundary conditions on the simulation results; • (3) to investigate sensitivity of model parameters on simulated results.

  14. Modelling • A CFD model based on Eulerian–Eulerian approach and modified k-e turbulence model. • Second-order scheme was used for all variables except the volume fraction equations, for which the QUICK discretization scheme was used.

  15. Results and discussion • The steady-state model can simulate the core-annulus flow more efficiently, which can eliminate the unrealistic sensitivity and consumes less computational resources .

  16. Inlet boundary conditions • Results show that in the fully developed region, the steady-state model is not sensitive to the three different inlet boundary conditions. So C is used for simulation

  17. Sensitivity study • These sensitivity analysis were investigated in this section, in which four key parameters including particle–particle restitution coefficient (es), particle-wall restitution coefficient(ew), specularity factor(ψ) and kinetic energy transfer coefficient(Cs) were considered.

  18. Conclusions • The steady-state model can simulate the core-annulus flow more efficiently, which can eliminate the unrealistic sensitivity. • In the fully developed region, the steady-state model is not sensitive to the three different inlet boundary conditions. • The sensitivity of the model predictions with respect to four parameters indicates that ew and ψ has weak influence on the correctly prediction of core-annulus flow, while the model remains a certain of sensitivity to es (1)and Cs(0.85).

  19. Thank You !

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