1. 5-9-B Cyclone Separators Cyclone separators are gas cleaning devices that  employ a centrifugal force generated by a spinning gas stream  to separate the particulate matter (solid or liquid) from the gas carrier. The operation depends upon the tendency (inertia) of particles to move in a straight line when the direction of stream is changed.

2. Two major classes of cyclone separators See overhead.

3. How particles separated from gas? A high rate of spin  Spinning gas fling  Centrifugal force fling the dust particles to the walls of cylinder and cone  The particle then slide down the wall and into the storage hopper  The cleaned gas gradually spiral downward …  The downward cleaned gas gradually reversed its downward and forms a smaller ascending spiral  A vortex finder tube extending downward into the cylinder aids in directing the inner vortex out of the device

4. Efficiency of cyclone separators Figure 5-16 Table 5-5

5. The difference in theoretical prediction and experimnental data See discussions on 4 points Reason: This is caused by the fact that cyclone, like the settling chamber, has a turbulent flow, although the large friction losses along the wall tend to dampen out the turbulence.

6. A more realistic approach to avoid a sharp cutoff as predicted in the previously derived theory (equation): to correlate data from cyclones with similar proportions (in size) and with respect to a cutoff size dp,50 Find out the cutoff size dp that gives 50% of efficiency  dp,50 dp,50 =

7. Significance of Figure 5-17

8. Example 5-8 A cyclone is designed with an inlet width of 12.0 cm and four effective turns. The inlet gas velocity is to be 15.0 m/s, and the particle density is 1.70 g/cm3. Estimate the particle size that will be with 50 percent efficiency, if the gas is air and its temperature 350K.

9. In review: Cyclone’s collection efficiency η col Why small particles are not captured efficiently?

10. Other factors that can improve cyclone’s efficiency