Some modeling and numerical aspects of the two-fluid simulation of the gas-solids flow in a CFB riser

Abstract

-The gas-solids flow in a CFB riser is simulated applying two-fluid modeling. Two different procedures are used for the calculation of the solids phase pressure and stress tensor: the traditional procedure and an algebraic version of the kinetic theory of granular flows. Three different numerical meshes and two different discretization schemes for the advective terms are used. Results are compared to available experimental data from the literature. The effects of the solids phase modeling procedure, advection discretization scheme, and mesh size are discussed.

Experimental and numerical study of pseudo-2D circulating fluidized beds

“…In the two-fluid model, the solid-phase momentum equation requires closure models for the solid stress tensor. These solid stresses can be modeled using empirical correlations, the KTGF, or a hybrid approach that employs both methods (Cabezas-Gomez et al, 2006). Application of the KTGF allows the user to determine the solid stress.…”

“…Thus, they are more appropriate for bubbling fluidized beds. Given the complexity of the partial differential equation, longer computational times and instabilities in the solution process, the algebraic form of the equation has been preferred by many authors for simulating bubbling fluidized beds (van Wachem et al, 1998;Cloete et al, 2013;Cloete, Johansen, & Amini, 2015) as well as risers (Cabezas-Gomez et al, 2006).…”

“…Such conditions occur in bubbling fluidized beds. However, because of its simplicity and stable behavior during calculations, the algebraic equation is frequently used in both bubbling fluidized beds (van Wachem et al, 1998;Cloete et al, 2013) and risers (Cabezas-Gomez, Silva, & Milioli, 2006). Here, we evaluate the effect of using the algebraic versus the partial differential equation for solving turbulent fluidization.…”

Effects of inter particle friction on the meso-scale hydrodynamics of dense gas-solid fluidized flows

“…The pressure-velocity coupling is solved through the SIMPLE algorithm. The numerical code of MFIX is fully described in (Syamlal et al 1993;Cabezas-Gómez et al 2006), and tested some of the discretization procedures for advective terms in MFIX, and found the Superbee procedure to provide the best results for the simulation of a particular riser flow. This procedure is followed in the current work.…”

Proposta de modelo não-paramétrico para quantificação de regimes de fluidização

“…A modelagem de dois fluidos estabelece as mudanças no momento e aceleração de parcelas fluídicas resultam de alterações de pressão e forças viscosas, originada da interação molecular. A viscosidade dinâmica da fase sólida é considerada como uma constante baseada em experimento, e a pressão de fase sólida é calculada a partir de funções envolvendo o módulo de elasticidade de colisões entre partículas e correlações empíricas [116].…”