Ergun CFB Software

Highly Charged Cyclones

As we mentioned above, the cyclone is a key tool in the CFB system. The suspension flow coming into the cyclone is highly loaded by solid particles and the separation phenomenon differs from simple dilute cyclones used in bubbling fluidization (please see "Cyclones" topic at Ergun BFB page). The HC Cyclones are always larger than standard cyclone to avoid "flooding".

The concept of HC Cyclone modeling can be resumed as follows :

1. As soon as the suspension enters the cyclone a large part of particles forms a kind of falling ribbon (flow part "1" on the figure beside). In this stepmore than 90 % of solids are separated just by contraction effect. The efficiency calculated from this first separation step is called "Primary Efficiency".
2. A part of the suspension is entrained in the central zone, much less loaded than the entering suspension. Some of the particles can be entrained up by the gas flow. The efficency of separation in this central zone is called (secondary efficiency).
3. Finally, a small part of the suspension may "by-pass" the system and covers the "roof" of the cyclone. The separation of these particles may be partly due to the surface of the vortex finder (exit tube).

One of the most major differences between the Highly Charged Cyclone and dilute cyclones is the important effect of suspension/wall friction factor. Some other difficulties come on with the population balance.

Ergun CFB Software has a powerful HC Cyclone modeling routine developed after the latest theories available in the scientific literature. The friction factor is first calculated from a diagram plotted by the program.

The results including efficiency, size distributions and pressure drop are presented on a graph as well as a simple text file.

Ergun Design Technology

Typical flow lines in a "Highly Cherged Cyclones"

Example of friction factor calculation diagram as plotted by Ergun CFB

Example of results presented in the graphical mode with interactive functionalities.

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