Presentation on theme: "5-9-B Cyclone Separators Cyclone separators are gas cleaning devices that employ a centrifugal force generated by a spinning gas stream to separate."— Presentation transcript:
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.
Two major classes of cyclone separators See overhead.
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
Efficiency of cyclone separators Figure 5-16 Table 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.
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 =
Significance of Figure 5-17
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.
In review: Cyclone’s collection efficiency η col Why small particles are not captured efficiently?
Other factors that can improve cyclone’s efficiency