Design considerations
- • Select either the high efficiency or high throughput design, depending on the performance required
• Obtain an estimate of the particle size distribution of the solids in the stream to be treated.
• Calculate the number of cyclone needed in parallel.
• Estimate the cyclone diameter for an inlet velocity of say 15 m/s. Then obtain the other cyclone dimensions from the graphs (refer to page 452, Sinnott, 2005 )
• Then estimate the scale up factor for the transposition of the figure. (refer to page 452 and 453, Sinnott, 2005 )
• Estimate the cyclone performance and overall efficiency, if the results are not satisfactory try small diameter.
• Calculate the cyclone pressure drop and check if it is within the limit or else redesign.
• Estimate the cost of the system and optimize to make the best use of the pressure drop available ( Sinnott, 2005 ).
Example 5.1 : Estimate the cut diameter and overall collection efficiency of a cyclone given the particle size distribution of dust from cement kiln. Particle size distribution and other pertinent data are given below (refer: Theodore, 2008 ).
Avg particle size in range dp , μm |
1 |
5 |
10 |
20 |
30 |
40 |
50 |
60 |
>60 |
Wt percent |
03 |
20 |
15 |
20 |
16 |
10 |
06 |
03 |
07 |
Gas viscosity = 0.02 Cp; Specific Gravity of the particle = 3.0
Inlet gas velocity of cyclone = 48 ft/sec
Effective number of turns within cyclone = 5
Cyclone diameter = 8 ft
Cyclone inlet width = 2 ft
Solution:
Cut size dpc can be calculated from the following equation
and collection efficiency as a function of the ratio of particle diameter to cut diameter can be obtained by
First determine the value of
....................
......................................= 2.92 × 10-5 ft
......................................= 8.9 µm