Page 264 - Air Pollution Control Engineering

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Wet and Dry Scrubbing 243

Solution

A data collection exercise for the purpose of preparing a permit application suitable for
submission to the appropriate authorities must accommodate the following: pretreatment
considerations, construction materials, pressure drop estimation, and actual Venturi size
estimation. The following is a data sheet suitable for this exercise.
Calculation Sheet for Venturi Scrubbers
A. HAP Characteristics—needed data
1. Flow rate (Q ) = acfm
e,a
2. Temperature (T ) = °F
e
3. Moisture content (M ) = %
e
4. Required collection (removal) efficiency (CE) = %
5. Mean particle diameter (D ) = µm
p
6. Particulate content = grain/scf
7. HAP content = % of total mass
B. Permit Review Data to be presented by applicant
1. Reported pressure drop (across Venturi) (P ) = in. H O
v 2
2. Pertinent performance curve for Venturi scrubber (from supplier)
3. Reported collection (removal) efficiency (CE) = %
C. Determination of Pretreatment Requirements
As previously discussed, for the Venturi principle to be applied to an air pollution control
need, the air being treated should be at 50 –100°F above its saturation (dew) temper-
ature. If the air to be treated does not meet this condition, then pretreatment of the air
will be required. Such pretreatment of the air will change two important design
parameters:
1. Maximum flow rate at actual conditions (Q ) = acfm
e,a
2. Temperature (T ) = °F
e
D. Projected Venturi Pressure Drop
The suppliers of the Venturi scrubber system supply the operating data curves (see
Fig. 5). These curves can be used to estimate the pressure drop, P , for the proposed
v
Venturi scrubber, at a given removal efficiency.
P = in. H O
v 2
Also previously noted, if this pressure drop exceeds 80 in. of H O, alternative control
2
technology needs to be considered, as the Venturi scrubber will most likely not
achieve the desired removal efficiency.
E. Proposed Material of Construction
Selection of material used to actually fabricate a Venturi scrubber is normally recom-
mended the system supplier. A useful first estimate of the type of material required can
also be made by consulting Table 14.
Material of construction =

F. Proposed Venturi Scrubber Sizing
Performance curves supplied by system suppliers may be derived for saturated emis-
sion stream flow rate (Q ). If so, Q may be determined:
e,s e,s
Q = [Q (T + 460) / (T + 460)] + Q (28)
e,s e,a e,s e w