93-328 AIR POLLUTION CONTROL
Review 2, 2005
True/false questions
Baghouse
1. During filtration, dry cake formed on the filter medium.
2. Filter medium does some filtering but major filtration job is performed by the dry
cake.
3. Main function of filter media is to support the dry cake.
4. The removal efficiency is generally a concern of the designer.
5. All test data points on a clean fabric can be used to obtain the slope and intercept
of the filter drag versus areal dust density.
6. The slope and intercept of the filter drag versus areal dust density from test data
can be used directly in operation conditions.
7. The net A/C will double if the cloth area is doubled.
8. The pressure drop in a baghouse depends on run time.
9. In a baghouse with N compartments, the flow rate through each compartment will
differ from the others.
10. Number of compartments in Table 6.3 in C&A refers to N-1.
11. Name five mechanisms by which fabric filters remove and retain particulate
matter.
12. The temperature limit of most baghouses is approximately:
100 F
300 F
500 F
1000 F
2000 F
Particulate scrubbers
13. The smaller the droplets, the higher the removal efficiency.
14. The impacting parameter is not a function of particle size.
15. The higher the water rate, the better.
16. The exit gas temperature is usually lower than that of the inlet.
17. The amount of liquid water remains constant.
18. The exit gas is usually saturated with water vapor.
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19. With on-site wastewater treatment, 100% of the water input to the scrubber can be
recycled.
20. At saturation, the wet bulb temperature equals dry bulb temperature.
VOC incinerators
21. Incineration of VOCs does not produce NOx.
22. Incineration of VOCs does require fuel.
23. List the three Ts in VOC incineration design. Why are they important? (short
answer)
24. What would likely be the concerns of a local community toward construction of a
PCB incinerator? (short answer)
Adsorption (fixed) bed
25. In carbon bed design, one can always use the amount of carbon determined by
mass to be adsorbed and the adsorption capacity of the carbon.
26. The exit VOC concentration is time-independent.
27. In a fixed bed adsorption system, one would need at least two beds.
28. Theoretically, can a biofiltration system be used to treat VOCs from carbon bed
regeneration?
Absorption
29. Wet scrubbers may not remove effectively VOCs with very high solubility.
30. Henry’s law constant is usually a function of temperature.
31. Wet scrubbers often operate above equilibrium.
32. In a counter flow absorption tower, too high a gas velocity will cause flooding.
33. For a SO2 scrubber, the aqueous reactions involving dissolved SO2 will enhance
gas phase SO2 removal.
Overall
34. Which of the following air pollution control devices has the lowest efficiency in
removing fine particles?
Settling chamber
Cyclone
ESP
Venturi Scrubber
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Fabric Filter
35. Cyclones can be made to collect particles more efficiently if one decreases inlet
gas velocity.
36. The charging of particles in an ESP occurs when the dust strikes the charging
electrode.
37. The pressure drop in an ESP is usually low. Thus, the operation cost is low as
well.
38. If a particulate removal system is altered to remove smaller particle diameters,
there will be a corresponding increase in the overall collection efficiency. (short
answer)
39. For given dust loading initially and two identical collectors in series, why is the
overall collection efficiency of the second collector usually less than the first.
(short answer)
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