filter
TRANSCRIPT
![Page 1: Filter](https://reader033.vdocument.in/reader033/viewer/2022052904/557d3eaad8b42af30d8b4e7f/html5/thumbnails/1.jpg)
Aerosol & Particulate Research Lab 110/03/2002
Fabric Filters
• Filtration• Fabric Selection• Fabric Cleaning• Air/Cloth Ratio, Filtration Velocity• Filtration Mechanisms• Pressure Drop and Design Consideration
Reading: Chap. 6
![Page 2: Filter](https://reader033.vdocument.in/reader033/viewer/2022052904/557d3eaad8b42af30d8b4e7f/html5/thumbnails/2.jpg)
Aerosol & Particulate Research Lab 210/03/2002
Filtration
Packing density/solidity
Fiber filter
porosity - 1 volumetotal
mefiber volu
For fiber filter, < 0.1For woven filter, ~ 0.3
Q: Do filters function simply as sieves (to collect particles larger than the sieve spacing)?
![Page 3: Filter](https://reader033.vdocument.in/reader033/viewer/2022052904/557d3eaad8b42af30d8b4e7f/html5/thumbnails/3.jpg)
Aerosol & Particulate Research Lab 310/03/2002
Theodore & Buonicore, Air Pollution Control Equipment, CRC Press, 1988.
![Page 4: Filter](https://reader033.vdocument.in/reader033/viewer/2022052904/557d3eaad8b42af30d8b4e7f/html5/thumbnails/4.jpg)
Aerosol & Particulate Research Lab 410/03/2002
Shaker Baghouse
Theodore & Buonicore, Air Pollution Control Equipment, CRC Press, 1988.
Frequency Several cycles/sMotion type Simple harmonic
or sinusoidalPeakacceleration
1-10 gravity
Amplitude Fraction to a fewinches
Mode Off-streamDuration 10-100 cycles, 30
s to a few minutesCommonbag diameter
5, 8, 12 in
Shaker Cleaning Parameters
Q: What are the common problems encountered?
![Page 5: Filter](https://reader033.vdocument.in/reader033/viewer/2022052904/557d3eaad8b42af30d8b4e7f/html5/thumbnails/5.jpg)
Aerosol & Particulate Research Lab 510/03/2002
Reverse-Air
Q: Pros and Cons?Cleaning dust on baghouse walls by traditional sledge-hammering
![Page 6: Filter](https://reader033.vdocument.in/reader033/viewer/2022052904/557d3eaad8b42af30d8b4e7f/html5/thumbnails/6.jpg)
Aerosol & Particulate Research Lab 610/03/2002
Reverse-Air Cleaning Parameters
Reverse-Jet
![Page 7: Filter](https://reader033.vdocument.in/reader033/viewer/2022052904/557d3eaad8b42af30d8b4e7f/html5/thumbnails/7.jpg)
Aerosol & Particulate Research Lab 710/03/2002
Pulse-Jet
Q: How can the blown-away particles by the on-line cleaning process be collected?Q: Felted fabric or woven fabric?
![Page 8: Filter](https://reader033.vdocument.in/reader033/viewer/2022052904/557d3eaad8b42af30d8b4e7f/html5/thumbnails/8.jpg)
Aerosol & Particulate Research Lab 810/03/2002
Air/Cloth Ratio
A
QV
Filtration velocity(average velocity)
Q: If thicker fabric is needed to sustain the high force, is its operating cost higher?
![Page 9: Filter](https://reader033.vdocument.in/reader033/viewer/2022052904/557d3eaad8b42af30d8b4e7f/html5/thumbnails/9.jpg)
Aerosol & Particulate Research Lab 910/03/2002
Filtration Mechanisms• Diffusion (Lee & Liu, 1982)
factor ichydrodynam Kuwabara 44
3ln
2
1
numberPeclet
158.2
2
0
3/2
Ku
D
UdPe
PeKu
f
D
Lee, K.W. & Liu, B.Y.H., Aerosol Sci. Technol.,1:47-61, 1982
Q: How does efficiency change wrt dp?Q: How to increase efficiency by diffusion?
http://aerosol.ees.ufl.edu/respiratory/section04.html
![Page 10: Filter](https://reader033.vdocument.in/reader033/viewer/2022052904/557d3eaad8b42af30d8b4e7f/html5/thumbnails/10.jpg)
Aerosol & Particulate Research Lab 1010/03/2002
• Impaction (Yeh & Liu, 1974)
4.0for 5.27)286.29(
18
2
)(
8.2262.0
02
0
2
RRRJ
d
UCd
d
UStk
Ku
JStk
f
cpp
f
I
f
p
d
dR
Yeh. H.C. & Liu, B.Y.H., J. Aerosol Sci., 5:191-217, 1974
Q: How to increase impaction efficiency? Q: How does efficiency change wrt dp?
(J = 2 for R > 0.4)
![Page 11: Filter](https://reader033.vdocument.in/reader033/viewer/2022052904/557d3eaad8b42af30d8b4e7f/html5/thumbnails/11.jpg)
Aerosol & Particulate Research Lab 1110/03/2002
• Interception (Krish & Stechkina, 1978)
2
2
)1(2
)2
1(1
11)1ln(2
2
1R
RR
Ku
RR
Krish, A. A. & Stechkina, I. B., “The theory of Aerosol Filtration with Fibrous Filters”, in Fundamentals of Aerosol Science, Ed. Shaw, D. T., Wiley, 1978.
Q: How to increase interception efficiency?
Fat Man’s Misery, Mammoth Cave NP
![Page 12: Filter](https://reader033.vdocument.in/reader033/viewer/2022052904/557d3eaad8b42af30d8b4e7f/html5/thumbnails/12.jpg)
Aerosol & Particulate Research Lab 1210/03/2002
• Gravitational Settling
• Total Single Fiber Efficiency
• Total Filter Efficiency
0
2
0
TS0
18
direction same in the V and for U )1(
U
gCd
U
VG
RG
cppTS
G
GRID
GRID
)1)(1)(1)(1(1
ff
Sd
HP exp1
)1(
4exp11
Sf: Solidarity factor
Q: How does the filter efficiency change wrt particle size?
![Page 13: Filter](https://reader033.vdocument.in/reader033/viewer/2022052904/557d3eaad8b42af30d8b4e7f/html5/thumbnails/13.jpg)
Aerosol & Particulate Research Lab 1310/03/2002
H = 1mm = 0.05
df = 2m
U0=10 cm/s
Q: Should we increase or decrease flow velocity in order to increase collection efficiency for (a) tobacco smoke, (b) cement dust?
![Page 14: Filter](https://reader033.vdocument.in/reader033/viewer/2022052904/557d3eaad8b42af30d8b4e7f/html5/thumbnails/14.jpg)
Aerosol & Particulate Research Lab 1410/03/2002
Parallel Flow
Operation
Q: How do you determine when to clean?
![Page 15: Filter](https://reader033.vdocument.in/reader033/viewer/2022052904/557d3eaad8b42af30d8b4e7f/html5/thumbnails/15.jpg)
Aerosol & Particulate Research Lab 1510/03/2002
Pressure Drop (Filter Drag Model)
spf PPPP VLVtKVK 21
Areal Dust Density LVtW
Filter drag
V
PS
WKKS 21
K2
K1
K1 & K2 to be determined empirically (resistance factor)Pf: fabric pressure dropPf: particle layer pressure dropPs: structure pressure drop
Time (min) P, Pa
0 150
5 380
10 505
20 610
30 690
60 990
Q: What is the pressure drop after 100 minutes of operation? L = 5 g/m3 and V = 0.9 m/min.
![Page 16: Filter](https://reader033.vdocument.in/reader033/viewer/2022052904/557d3eaad8b42af30d8b4e7f/html5/thumbnails/16.jpg)
Aerosol & Particulate Research Lab 1610/03/2002
Time to clean
ccrf tttNt )(
N
QQN Flow rate
11 N
QQN
Filtering velocity
CC
NN NA
Q
A
QV
CC
NN AN
Q
A
QV
)1(1
1
Q: What are the parameters that affect our decision on the number of compartments to be used?
![Page 17: Filter](https://reader033.vdocument.in/reader033/viewer/2022052904/557d3eaad8b42af30d8b4e7f/html5/thumbnails/17.jpg)
Aerosol & Particulate Research Lab 1710/03/2002
Areal dust density
))(1( 1 cNrNj LtVLtVNW
Filter drag
jj WKKS 21
Actual filtering velocity
1 NNj VfVPressure drop
jjmj VSPP
N 1/ NfN VVf
3 0 . 8 74 0 . 85 0 . 7 67 0 . 7 1
1 0 0 . 6 71 2 0 . 6 51 5 0 . 6 42 0 0 . 6 2
2 0
![Page 18: Filter](https://reader033.vdocument.in/reader033/viewer/2022052904/557d3eaad8b42af30d8b4e7f/html5/thumbnails/18.jpg)
Aerosol & Particulate Research Lab 1810/03/2002
Ex. Calculate the max pressure drop that must be supplied for the following baghouse for a filtration time of 60 minutes: K1 = 1 inch H2O-min/ft, K2 = 0.003 inch H2O-min-ft/grain, tc = 4 min, 5 compartments, L = 10 grain/ft3, Q = 40000 ft3/min, Ac = 4000 ft2/compartment.
![Page 19: Filter](https://reader033.vdocument.in/reader033/viewer/2022052904/557d3eaad8b42af30d8b4e7f/html5/thumbnails/19.jpg)
Aerosol & Particulate Research Lab 1910/03/2002
Quick Reflection