Page 130 - Air Pollution Control Engineering

03_chap_wang.qxd 05/05/2004 12:48 pm Page 109
Cyclones 109

The gas velocity at the exit [Eq. (6)] is
3
v = ( 4 0.0906 m s )
o 2
π (0.151 m )
v = 5.1m s
o

m
The values of α [Eq. (7)] and h [Eq. (4), as D > B] are given by
e
. (
−
α = 11 20 .060 m 0 .302 m )
.
α = 076
h m = (1.208 m − 0.453 m )(0.302 m − 0.151 m ) + (0.453 m − 0.151 m )
0.302 m − 0.113 m
h m = 0.905 m
m
Once α and h only depend on the cyclone dimensions, their values remain constant for
the entry velocities of 10, 15, and 20 m/s, as well as the value of λ (0.02).
The maximum tangential velocity [Eq. (5)] is
)(
 ( 0.151m 2 0.302 m 0.060 m)π 
−
ν = 5.1m s  
−
tmax ( [ )( )( (
  2 0.151 m 0.060 m 0.76)] + 0.905 m 0.302 m 0.060 m)( ) π 0.02  
ν tmax = 10.6 m s
m
Now v /v can be calculated as a function of particle diameter [Eq. (2)]:
ts ts
v ( π.0 905 m )(860kg m 3 )( .10 6m s ) 2 D 2
ts = i
3
( .×810kgms0
v m 91 −5 )( .0906m s )
ts
ν
ts = 1.8718 × 10 10 D 2 , with D in meters.
ν m i i
ts
The collection efficiency [Eq. (1)] can therefore be written as
1
η = [ 1 + . (1 8718 ×10 D i ) −32. ] , with D in meters.
i
i
10
2
For the other entry velocities, the results are as follows:
For v = 15 m/s,
i
3
m 3600s
3
Q = 0.139 = 500.4 m h
s 1 h
v = 7.8 m s
o
v tmax = 16.3 m s