Geoscience Reference
In-Depth Information
Solution:
To calculate the number of bags needed (
N
), we need the total required surface area of the
bags and the surface area of each bag. Calculate the total required surface area of the bags
A
c
in ft
2
:
A
v
=
Q
/
v
f
where
A
v
= Total surface area of the bags.
Q
= Volumetric flow rate.
v
f
= Filtering velocity.
Thus,
A
v
=
Q
/
v
t
= 50,000/10 = 5000 ft
2
Calculate the surface area of each bag (
A
) in ft
2
:
A
= π ×
D
×
h
where
A
= Surface area of a bag.
D
= Diameter of the bag.
h
= Length of the bag.
Thus,
A
= π ×
D
×
h
= π × 1.0 × 15 = 47.12 ft
2
Finally, calculate the number of bags
N
required:
N
=
A
c
/
A
= 5000/47.12 = 106
Now calculate the required frequency of cleaning:
∆
p
= 0.2
v
f
+ 5
c
(
v
f
)
2
t
Because ∆
p
is given as 8.0 in. H
2
O, the time since the bags were cleaned is calculated by solving
the above equation:
5.0 grains/ft
3
= 0.0007143 lb/ft
3
and ∆
p
= 0.2
v
f
+ 5
c
(
v
f
)
2
t
8.0 = (0.2 × 10) + (5 × 0.0007143 × 10
2
)
t
Thus,
t
= 16.8 min.
■
EX AMPLE 17.14
Problem:
An installed baghouse is presently treating a contaminated gas stream. Suddenly some
of the bags are broken. We are now requested to estimate the new outlet loading of this baghouse
system (USEPA, 1984b, p. 88).
Given:
Operation conditions of the system = 60°F, 1 atm
Inlet loading = 4.0 grains/acf
Outlet loading before bag failure = 0.02 grains/acf
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