Investigation of behaviors of the circulating fluidized bed

- The circulating fluidized bed with internal horizontal baffles has been investigated.
- Eulerian-Eulerian approach with Gidaspow gas-solid drag model and standard k-e model.
- Mass of catalyst in the empty space between the baffles and in the baffles area.
- Evaluation of residence time for catalyst particle in the column versus flow rate.

The circulating fluidized bed, separated by horizontal baffles, was studied both experimentally and numerically by CFD methods. The pressure distribution in a large-scale cold-flow column with a diameter of 700 mm with a circulating fluidized bed of a microspheric catalyst was measured experimentally for the superficial velocity range from 0.05 to 1.0 m/s. The column was sectioned in height by four rows of horizontal baffles made of several angle bars. For this column design 3D CFD simulations were performed based on the Eulerian-Eulerian approach (two-fluid model) with standard closures and using a coarse computational grid.Comparison of the results of the experiment and transient simulations showed that simulation allows estimating the pressure distribution in a fluidized gas-solid apparatus with an error not exceeding 5%. This prediction accuracy can be sufficient for important practical applications, for example, for the calculation and design of the apparatus or the choice of the design of distributive baffles.The pressure distribution over the height of the column is largely determined by the distribution of the catalyst particles inside column. For example, the contribution of the particle weight to the static pressure is approximately 96% for the superficial velocity Wo ∼ 0.1 m/s. Therefore, this kind of simulation can provide useful information for the distribution of solid particles in a fluidized bed apparatus. This is important for a large number of users of commercial CFD packages, which are engaged in the design of devices that provide optimal hydrodynamic conditions.

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