Page 291 - APPLIED PROCESS DESIGN FOR CHEMICAL AND PETROCHEMICAL PLANTS, Volume 1, 3rd Edition

Mechanical Separations 261

c. Select cylindrical shell diameter, D with two consid- Efficiency
0
erations in mind:
Typical estimating efficiencies are given in Figures 4-46
• Large diameter reduces pressure drop and 4-47. Note the curves indicate how much dust of each
• Small diameter has higher collection efficiency for particle size will be collected. The efficiency increases as
the same entrance conditions and pressure drop. the pressure drop increases; that is, a smaller separator
might have a higher efficiency due to the higher gas
d. The length of the inverted cone section, Zc, is critical, velocities and increased resistance than a larger unit for
although there is no uniformity in actual practice. The the same gas flow. For example, there are several curves
dimensions suggested in Figure 4-41 are average. of the typical shape of Figure 4-46, with each curve for a
definite resistance to flow through the unit.

lnltl lnltl The pressure drop in a typical cyclone is usually
i rarely exceeds 10 inches water for single units. The API
\nit! between 0.5 and 8 inches of water. It can be larger, but
study [7] summarizes the various factors. Lapp le [ 13, 16]
gives calculation equations, but in general the most reli-
Oulltl able pressure drop information is obtained from the man-
ufacturer.
Figure 4-40. Centrifugal separator applications. By permission, Cen- Here is how the pressure drop may be estimated.
trlflx Corp.

For the typical cyclone of Figure 4-41 [13]
A A (a) Inlet velocity head based on inlet area:
L _ _j
hui = 0.003p v( 2 (4-53)

- I I
Gas
In
I
__ .J. __ ..L
Sc I
�-D,-..JT I I -.. aT-l'AH
W1= Dc/4 Le DUIT CHAHNll
D,• Dc/2 I
He= Dc/2 I I ---- IHIIT ro•
oun lADIN GASU
Lc•2 De ---De-- I
Sc• Dc/8 I I
Zc•2 De 1-------J-t
Jc• Arbitrary, I
Usually Dc/4 I
I
I
I
I
I
fc
I
I
I
I
I
Section A-A I I
--1..
Jc
Dust J Out
Figure 4-41. Cyclone separator proportions-dust systems. By per-
mission, Perry, J. H., Chemical Engineers Handbook, 3rd Ed., Figure 4-42. Van Tongeran dust shave-off design. Courtesy of Buell
McGraw-Hill Company, 1950. Engineering Co.