Ergun CFB Software

Flow Pattern Study

The study of the "Flow Pattern" in the riser of the CFB is one of the points providing important information like "Flow Regime", solid velocity and volume fraction profiles, wall down flow rate, etc.

An important number of works are published in the scientific literature on the modeling of CFB risers. The state of art in CFD (Computational Fluid Dynamics) is not yet enough riche to provide quatitative results. However, a number of researchers propose several valuable models based on various physical concepts or simply on some correlations.

Many of these models are focused on one or few special points of the "Flow Pattern" and do not provide all the desired information on the flow.

Note that the flow regime depends essentially on the fluidization velocity. At low velocities there is only a dense (bubbling or turbulent) bed with some particles entrained. At an intermediate regime (that of Power Stations) a dense bed is formed at the bottom and a "clustered lean bed" appears on the upper part. For higher velocities (like FCC Risers) the dense bed at the lower part disappears and the flow becomes more homogeneous. However, the flow conserves "Radial" profiles of solid velocity, flow rate and volume fraction.

Main features provided by Ergun CFB Software are :

• Bed Structure definition (model1)
• Bed Characteristics (at lower and upper regions)
• Radial profiles calculations (model2)
• Global correlative estimation of solid flow rate and solid volume fraction (model3)
• Wall down-flow characteristics

The figures on the right are extracted from some of numerous figures and diagrams provided by the program.

Ergun Design Technology

Examples of flow patterns calculated with various operating velocities

Several models are used to calculate diverse properties of the flow

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