Axial gas and solids mixing in a down flow circulating fluidized bed reactor based on CFD simulation

Khongprom, Parinya; Aimdilokwong, Archwit; Limtrakul, Sunun; Vatanatham, Terdthai; Ramachandran, P.A.

doi:10.1016/j.ces.2012.01.020

Cited by 31 publications

(18 citation statements)

References 27 publications

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“…The Euler‐Euler approach solves the transient advection‐diffusion of a passive scalar field using the fluid velocity profile. This can be achieve while the CFD simulations are running or during post‐processing, since the scalar used to calculate the RTD does not affect the flow patterns . However, since the advection‐diffusion equation is hyperbolic at a high Peclet number, proper upwinding must be used to ensure that no oscillations occur in the passive scalar field.…”

Section: Applicationsmentioning

confidence: 99%

Experimental methods in chemical engineering: Residence time distribution—RTD

2020

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Reactor performance, solids‐(gas)‐mixing, flow through porous media, distillation columns, or through granulators improve as the fluid dynamics approach ideal plug flow. The residence time distribution (RTD) is a diagnostic measure of how close fluid flow approaches ideal conditions. The technique introduces a step change to the inlet concentration—a Dirac‐δ function, Heaviside step function, or a rectangular pulse (bolus)—while high frequency detectors monitor the concentration along the vessel and/or at the exit. The effluent concentration profile spreads due to the variance in the process lines leading to the vessel and at the exit, the detector response, and the system. We quantify how much each of these contributes to the overall variance in a fluidized bed with 9 g of fluid cracking catalyst in 8 mm diameter quartz tubes. The injection variance is lowest for a GC sample loop configuration, compared to a 3‐way valve or 4‐way valve geometry. RTD measurements detect bypassing due to dead zones in vessels and the axial‐dispersion model and continuous stirred‐tank model to characterize deviation from plug flow. However, when the contribution to variance from the ancillary lines and detector is large compared to the system, the uncertainty in the model parameters is high. Research on RTD fundamentals concentrate on boundary conditions while, here, we focus on experimental errors: mechanical, physicochemical mathematical, and instrumental.

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Section: Applicationsmentioning

confidence: 99%

Experimental methods in chemical engineering: Residence time distribution—RTD

2020

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“…An Eulerian-Eulerian approach to CFD has been successful to describe the hydrodynamics of gas-solid systems. [11][12][13] Xu et al (2012) 14 and Yao et al (2014) 15 applied CFD to polypropylene in a uidized bed reactor. Li et al (2016) 16 used a computational uid dynamics-discrete element model for studying temperature variation in uidized beds.…”

Section: Introductionmentioning

confidence: 99%

Heat transfer effect in scaling-up a fluidized bed reactor for propylene polymerization

et al. 2018

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“…Because of its importance, researchers have covered this issue in many studies [4][5][6][7]. Designing and making the large-scale reactor generally go through the several steps of scale-up process.…”

Section: Introductionmentioning

confidence: 99%

“…On the other hand, utilizing computational fluid dynamics (CFD) for predicting the behavior of CFB reactor saves up considerable expense required to experiment and collect data. Hence, utilizing CFD can be quite useful as it supplements the limited experiment data in scale-up process [5].…”

Section: Introductionmentioning

confidence: 99%

“…For example, the study of hydrodynamic behavior of CFB riser to verify a more accurate inlet boundary condition has been carried out [4] and systematical analyses on the axial dispersion and mixing behavior of gas and solid in a downer reactor have been made [5]. Chalermsinsuwan et al [7] studied the effects of various modeling parameters in the CFB downer.…”

Section: Introductionmentioning

confidence: 99%

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Study of hydrodynamic characteristics in a circulating fluidized bed gasifier for plastic waste by computational fluid dynamics modeling and simulation

Lee

Choi

Seo

2014

J Mater Cycles Waste Manag

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For designing an efficient circulating fluidized bed reactor, understanding the complex hydrodynamic characteristics in the reactor is required. Hence, in the present study, the modeling and simulation of the circulating fluidized bed gasifier using plastic waste were carried out with Eulerian-Granular approach. Several cases were investigated as changing superficial gas velocities or sizes of plastic waste particle. Firstly, cases were examined with four different velocities when the particle diameter is 1 mm. At the gas velocity of 6 or 8 m/s, gas volume fraction is more than 95 % throughout the reactor and particle velocity has positive value overall. Therefore, a circulating fluidized bed seems to be formed in both cases. Comparing those two cases, better solid mixing can be expected considering the mass fraction and solid velocity at the superficial gas velocity of 6 m/s. Thus this case was further studied for the effect of particle size. As the diameters of plastic waste particle are 1 or 3 mm, it is considered that a circulating fluidized bed is formed. And plastic waste and sand particles are well mixed throughout the reactor. However, the particle diameter increases over 3 mm then, it is very hard to maintain circulating fluidization condition. List of symbols dParticle diameter (m) F Coefficient for interphase drag force (kg m -3 s -1 ) gGravitational acceleration (m s -2 ) P Pressure (pa) S sj jth solid phase stress tensor (Pa) V Velocity vector (m s -1 )Greek letters e Void fraction q Density (kg m -3 ) s g Deviatoric stress tensor for gas phase (Pa)

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Axial gas and solids mixing in a down flow circulating fluidized bed reactor based on CFD simulation

Cited by 31 publications

References 27 publications

Experimental methods in chemical engineering: Residence time distribution—RTD

Experimental methods in chemical engineering: Residence time distribution—RTD

Heat transfer effect in scaling-up a fluidized bed reactor for propylene polymerization

Study of hydrodynamic characteristics in a circulating fluidized bed gasifier for plastic waste by computational fluid dynamics modeling and simulation

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