EMMS-based Eulerian simulation on the hydrodynamics of a bubbling fluidized bed with FCC particles

Wang, Junwu; Liu, Yaning

doi:10.1016/j.powtec.2009.09.022

Cited by 60 publications

(37 citation statements)

References 26 publications

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“…Cruz et al (2006) proposed a CFD model in which solids accumulation was observed in wall regions, redirecting the gas to the central region of the equipment, a behavior also observed during the present study. A similar profile for radial particle velocity using an EMMS drag model approach was also obtained by Wang and Liu (2010). From the present study, it can be inferred that the heterogeneity caused by the EMMS model led to qualitative differences between radial particle velocity profiles between the two models tested.…”

Section: Resultssupporting

confidence: 81%

Evaluation of Biomass Gasification Variables Considering Different Drag Model Approaches

Braga¹,

Béttega²,

Lopes³

2018

Enci Bio

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Energy use and generation, and their effects on the environment, more than ever deserve attention nowadays. Studies and research must be constantly carried out in order to optimize different kinds of energy-related processes. In the chemical engineering context, biofuels emerge as a good alternative to fossil fuels, and one interesting process to obtain them is biomass gasification. The aim of this study was to evaluate how two different drag model approaches could influence some aspects of biomass gasification, such as solids volume fractions and radial particle velocities profiles, and also product mole fraction at the gasifier outlet, considering a circulating fluidized bed. The findings suggest that there was no significant difference in product mole fraction at the gasifier outlet when comparing the results obtained for both drag models. On the other hand, solids volume fraction along bed height, and radial particle velocity, showed some differences and presented a qualitative agreement with the literature. KEYWORDS: CFD, biomass gasification, drag models. AVALIAÇÃO DE VARIÁVEIS DO PROCESSO DE GASEIFICAÇÃO DE BIOMASSA CONSIDERANDO DIFERENTES MODELOS DE ARRASTE RESUMOO uso e geração de energia e seus efeitos sobre o meio ambiente, mais do que nunca, merecem atenção nos dias de hoje. Estudos e pesquisas devem ser realizados constantemente para otimização de todos os diferentes tipos de processos relacionados à energia. No contexto da Engenharia Química, os biocombustíveis surgem como uma boa alternativa para substituição dos combustíveis fósseis, e um processo interessante para obter esse tipo de combustível é a gaseificação de biomassa. O objetivo deste estudo foi avaliar como duas diferentes abordagens de modelos de arraste poderiam influenciar em alguns aspectos da gaseificação de biomassa, como em perfis de frações volumétricas de sólidos e velocidades radiais de sólidos, bem como também na fração molar de produtos na saída do gaseificador, considerando um leito fluidizado circulante. Os resultados sugerem que não houve diferença significativa na fração molar dos

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Section: Resultssupporting

confidence: 81%

Evaluation of Biomass Gasification Variables Considering Different Drag Model Approaches

Braga¹,

Béttega²,

Lopes³

2018

Enci Bio

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“…These results evidence a clear resemblance in the particle recirculation patterns obtained in simulation and experiments, but it appears that the simula tions over predict the modulus of the particle velocity vectors for small superficial velocities (U/U mf ¼1.65 in Lindborg et al, 2007), and that the prediction of the vertical position of the recirculation centre is not completely satisfactory (Hosseini et al, 2010). Ahuja and Patwardhan (2008), for U/U mf ¼5.6, as well as Wang and Liu (2010), this last study using FCC particles, compared their two dimensional simulation results with three dimensional experiments and found acceptable agreement in the radial pro files of velocity. Very recently, Li et al (2010) compared the experimental results from the work done by Laverman et al (2008) in a pseudo 2D fluidized bed with 2D and 3D simulations using the drag model of Gidaspow.…”

Section: Introductionmentioning

confidence: 61%

Comparison between two-fluid model simulations and particle image analysis & velocimetry (PIV) results for a two-dimensional gas–solid fluidized bed

Hernández-Jiménez

Sánchez-Delgado

Gómez-García

et al. 2011

Chemical Engineering Science

109

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a b s t r a c tThis work compares simulation and experimental results of the hydrodynamics of a two dimensional, bubbling air fluidized bed. The simulation in this study has been conducted using an Eulerian Eulerian two fluid approach based on two different and well known closure models for the gas particle interaction: the drag models due to Gidaspow and Syamlal & O'Brien. The experimental results have been obtained by means of Digital Image Analysis (DIA) and Particle Image Velocimetry (PIV) techniques applied on a real bubbling fluidized bed of 0.005 m thickness to ensure its two dimensional behaviour. Several results have been obtained in this work from both simulation and experiments and mutually compared. Previous studies in literature devoted to the comparison between two fluid models and experiments are usually focused on bubble behaviour (i.e. bubble velocity and diameter) and dense phase distribution. However, the present work examines and compares not only the bubble hydrodynamics and dense phase probability within the bed, but also the time averaged vertical and horizontal component of the dense phase velocity, the air throughflow and the instantaneous interaction between bubbles and dense phase. Besides, quantitative comparison of the time averaged dense phase probability as well as the velocity profiles at various distances from the distributor has been undertaken in this study by means of the definition of a discrepancy factor, which accounts for the quadratic difference between simulation and experiments The resulting comparison shows and acceptable resemblance between simulation and experiments for dense phase probability, and good agreement for bubble diameter and velocity in two dimensional beds, which is in harmony with other previous studies. However, regarding the time averaged velocity of the dense phase, the present study clearly reveals that simulation and experiments only agree qualitatively in the two dimensional bed tested, the vertical component of the simulated dense phase velocity being nearly an order of magnitude larger than the one obtained from the PIV experiments. This discrepancy increases with the height above the distributor of the two dimensional bed, and it is even larger for the horizontal component of the time averaged dense phase velocity. In other words, the results presented in this work indicate that the fine agreement commonly encountered between simulated and real beds on bubble hydrodynamics is not a sufficient condition to ensure that the dense phase velocity obtained with two fluid models is similar to that from experimental measurements on two dimensional beds.

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“…One of the possibility is application of the Energy-Minimization MultiScale (EMMS) technique, which has been presented in Ref. [4]. In works [5] and [6] the EMMS technique has been future extended and used for modelling particle transport in large scale industrial boilers, where good accuracy of the model has been presented.…”

Section: Introductionmentioning

confidence: 99%

Numerical simulations of the industrial circulating fluidized bed boiler under air- and oxy-fuel combustion

Adamczyk

Kozołub

Klimanek

et al. 2015

Applied Thermal Engineering

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h i g h l i g h t s g r a p h i c a l a b s t r a c tHybrid Euler-Lagrange approach was used for modelling particle transport, air-and oxy-fuel combustion process. Numerical results were validated against measured data. The influence of different boiler operating conditions on calculated temperature profile was investigated. New strategy for resolving particle transport in circulating fluidized bed was shown. a b s t r a c tMeasured and numerical results of air-fuel combustion process within large scale industrial circulating fluidized bed (CFB) boiler is presented in this paper. For numerical simulations the industrial compact CFB boiler was selected. Numerical simulations were carried out using three-dimensional model where the dense particulate transport phenomenon was simultaneously modelled with combustion process. The fluidization process was modelled using the hybrid Euler-Lagrange approach. The impact of the geometrical model simplification on predicted mass distribution and temperature profiles over CFB boiler combustion chamber two kinds of geometrical models were used, namely the complete model which consist of combustion chamber, solid separators, external solid super-heaters and simplified boiler geometry which was reduced to the combustion chamber. The evaluated temperature and pressure profiles during numerical simulations were compared against measured data collected during boiler airfuel operation. Collected data was also used for validating numerical model of the oxy-fuel combustion model. Stability of the model and its sensitivity on changes of several input parameters were studied. The comparison of the pressure and temperature profiles for all considered cases gave comparable trends in contrary to measured data. Moreover, some additional test was carried out the check the influence of radiative heat transfer on predicted temperature profile within the CFB boiler.

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EMMS-based Eulerian simulation on the hydrodynamics of a bubbling fluidized bed with FCC particles

Cited by 60 publications

References 26 publications

Evaluation of Biomass Gasification Variables Considering Different Drag Model Approaches

Evaluation of Biomass Gasification Variables Considering Different Drag Model Approaches

Comparison between two-fluid model simulations and particle image analysis & velocimetry (PIV) results for a two-dimensional gas–solid fluidized bed

Numerical simulations of the industrial circulating fluidized bed boiler under air- and oxy-fuel combustion

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