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Three-Dimensional Gas-Solid Fluidized Bed Simulation Applying the Cfd Technique

Milton Mori1, Fabio Marini2, Maria das Grašas E. Silva2, and Maximilian J Hodapp3. (1) School of Chemical Engineering, University of Campinas, UNICAMP, R. Albert Einstein 500, Campinas, Brazil, (2) Dpq, University of Campinas, UNICAMP, R. Albert Einstein 500, Campinas, Brazil, (3) Chemical Engineering, University of Campinas, UNICAMP, R. Albert Einstein 500, Campinas, Brazil

Fluidized beds are widely used in many operations in chemical, metallurgical, energy generation and especially in petrochemical industries. Major applications are fluid catalytic cracking (FCC) risers and CFB combustors. No analytical tools that describe the influences of complex geometries, chemical reaction, internal reflux and heat transfer on the flow pattern in fluidized beds are available. With the increase in the availability of computers, the application of mathematical models to predict the behavior of a fluidized bed follow the same trend, and several models have been proposed.

In this work, a three-dimensional two-phase flow model based on kinetic theory of granular flow (KTGF) was used to predict the behavior of a gas-solid fluidized bed. The model is based on a Eulerian description of the two phase, gas and particles, and is composed of a set of mass conservation and momentum equations for each phase. In this model, turbulence k-epsilon model and multiphase mixture are contemplated. In order to describe the behavior of several particles in a continuum, the kinetic theory of granular flow was used. This approach has gained attention and its use in eulerian simulations has increased. The kinetic theory of granular flow is based on the kinetic theory of gases, first developed by Chapman e Cowling (1970). In this theory, the inter-particle interactions are taken into account, by adding the contribution of collisions between particles, Jenkins e Savage (1983), which are the main mechanism of transport due to particulate phase properties.

In this work, the geometry and numerical mesh were generated using ANSYS ICEM CFD software and the set of partial differential equations was discretized and solved using CFX. Simulation data were verified against data found in Samuelsberg e Herjtager (1996), who used a cold flow laboratory circulating fluidized bed and simulated a two dimensional model. The particle velocity was measured using a laser Doppler anemometry in that experimental study.

Results using this model have shown that the model agrees with the experimental data, and predicts a flow behavior similar to that found experimentally. It predicts the core annulus flow, wich is known from literature. The simulations were performed in three different values of velocity.