Implementação de modelo de fechamento em risers de FCC atraves de codigo comercial CFD

AUTOR(ES)
DATA DE PUBLICAÇÃO

2001

RESUMO

This work concerns in a study about a gas-solid flow (the gas mixture is air; the solid is catalyst particles) in the FCC riser. The riser is treated like a pipe without axis symmetry. This treatment allows the visualization of some of mass and momentum transfer phenomena through the center of pipe that cannot be predicted in a axisymmetrical approach. The geometry uses two dimensions: the axial and the radial direction. In this geometry, to obtain mixing at the entrance, three inlets allow to simulate the 3D effects of the cylindrical riser of the experiment. The inlets are: two symmetrical ones with a mixture gas-solid and one with a gas stream. This entrance scheme permits the interchange of the properties between the two half of the riser. The mathematical model is closed by the Kinetic Theory of Granular Flow. This theory calculates some solid properties hard to estimate as viscosity. Other property that arises from the Kinetic Theory is the solid pressure. These parameters, with reasonable values, are important to obtain a coherent flow field. The transport equation presented here is in its statical formo It means that the original partial differential equation is reduced to a quadratic algebraic equation. Besides, extra forces are tested in order to predict agglomeration and segregation motion of particles. These movement are the base of downflow near the walls. The forces tested are the Saffman lift force and the pressure force. The first one have its influence around the riser center in order to radially push the particles to walls. The second is significant where the solid concentration field have high variations. The final result of this modeling is a good prediction of experimental data from KNOWL TON et aI. (1995)

ASSUNTO(S)

craqueamento modelos matematicos teoria cinetica da materia

ACESSO AO ARTIGO

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