ASSIGNMENT 9
1. Circle the correct answer or fill in the blank.
a) Which of the following air pollution control devices has the lowest efficiency in removing fine particles?
o Settling chamber
o Cyclone
o ESP
o Venturi Scrubber
o Fabric Filter
b) Increased efficiency of particulate removal system is normally accompanied by a decrease in efficiency. ( TRUE / FALSE) : ______
c) The charging of particles in an ESP occurs when the dust strikes the charging electrode. ( TRUE / FALSE) : ______
d) The temperature limit for bag houses is approximately:
o 100 oF
o 300 oF
o 500 oF
o 1000 oF
o 2000 oF
e) Cyclones can be made to collect particles more efficiently if one decreases inlet gas velocity. ( TRUE / FALSE) : ______
2. An ESP is designed to treat 500,000 acfm with 98.5% efficiency. Assuming an effective drift velocity of 0.1 m/s, calculate the required plate area and the number of plates. The plate size is 6m by 3m (height by length).
A) 1.05E05ft2, 5833
B) 1.05E03ft2, 5833
C) 0.05E05ft2, 4634
D) 1.05E05ft2, 4634
3. The efficiency of an ESP is 98%. The efficiency of the ESP drops to 92% as a result of flow rate changes. The ratio of flow rates for the above situation is (use appropriate assumptions)
A) 0.792
B) 1.792
C) 1.296
D) 0.324
4.The efficiency of an ESP is 98%. The efficiency of the ESP drops to 92% as a result of flow rate changes. Calculate the ratio of flow rates for the above situation. Use appropriate assumptions.
5. A model baghouse follows the filter drag model
S = Ke +KsW
Where, Ke = 0.5 " H2O/(ft/min)
Ks = 0.0011 " H2O-ft-min/gr
The pressure drop for a full scale baghouse after 30 minutes of operation on an air stream with a dust loading of 27 gr/ft3 and an air-to-cloth ratio of 3.0 ft/min
A) 6 inches
B) 7 inches
C) 8 inches
D) 9 inches
6. From the following test data, the values of Ks and Ke for the filter drag model are
Limestone Dust Loading / 1.00 g/cumFabric Area / 1.00 sqm
Air Flow Rate / 0.80 cum/min
Time, min / 5 / 10 / 15 / 20 / 25 / 30
Filter Delta P, Pa / 322 / 490 / 542 / 602 / 641 / 725
(answers in units of min-1 and (Pa-min)/m)
A) 75.68, 15.32
B) 125.89, 31.48
C) 75.68, 31.48
D) 125.89, 15.32
7. An electrostatic precipitator with a specific collecting area of 400 ft2/1000 acfm and an applied voltage of 50 kV has a wire to plate spacing of 0.115 m. The drift velocity and the collection efficiency of the electrostatic precipitator for 0.5 micrometer diameter particles at 500o K are
(assume that the dielectric constant D is 6)
A) 0.033m/s, 92.82 %
B) 0.33m/s, 92.82 %
C) 0.033m/s, 82.82 %
D) 0.33m/s, 82.82 %
8. Water is introduced into the throat of a venturi scrubber. The air velocity through the scrubber is 450 fps and the liquid to gas ratio is 7.48 gal/1000 actual ft3.
The working temperature for the process is 220o F. The throat area is 180 in2. The pressure drop, penetration and efficiency for the given input values are
(The density of air can be taken as 0.072 lb/ft3. Use the Hesketh model for calculations.)
A) 48.10 in of water, 0.0136, 98.64%
B) 48.10 in of water, 0.136, 98.64%
C) 48.10 in of water, 0.0136, 78.64%
D) 48.10 in of water, 0.136, 78.64%
9. A cyclone has been designed with an inlet width of 10 cm and an inlet height of 6 cm. The height of the main upper cylinder is 16 cm and the height of the lower
cone is 16 cm. The inlet gas velocity is 16 m/s and the particle density is 1.6 gm/cc. The working temperature of the process is 400o K. The particle
size that will be collected with 50 percent collection efficiency is
A) 5.66um
B) 4.66um
C) 3.66um
D) 6.66um
10. An electrostatic precipitator has a collection efficiency of 99 percent and the mean inlet gas velocity is 2 m/s. The applied voltage is 60 kV and the wire to plate
spacing is 0.15 m. The drift velocity, specific collecting area, length of the collecting electrode and particle penetration of the electrostatic precipitator
for 1 micrometer diameter particles at 420o K are
(assume that the dielectric constant D is 5)
A) 0.050m/s, 463.72 sqft/1000acfm, 5.95m, 0.01
B) 0.50m/s, 463.72 sqft/1000acfm, 5.95m, 0.01
C) 0.050m/s, 363.72 sqft/1000acfm, 5.95m, 0.01
D) 0.50m/s, 363.72 sqft/1000acfm, 5.95m, 0.01
11. Water is introduced into the throat of a venturi scrubber at the rate of 0.001 m3/ m3 of gas flow. The air velocity through the scrubber is 410 fps and the liquid to gas ratio is 7.48 gal/1000 actual ft3. The working temperature for the process is 170o F. The parameter f has a value of 0.25, particle diameter is 1
micrometer and the particle density is 1.7 g/cc. The pressure drop, penetration and efficiency for the given input values are
(use the Calvert model for calculation)
A) 63.36 in. of water, 0.0558, 94.42%
B) 63.36 in. of water, 0.558, 94.42%
C) 63.36 in. of water, 0.558, 84.42%
D) 63.36 in. of water, 0.0558, 84.42%
12. A cyclone has been designed with an inlet width of 12 cm and an inlet height of 6 cm. The height of the main upper cylinder is 20 cm and the height of the lower
cone is 20 cm. The inlet gas velocity is 15 m/s and the particle density is 1.7 g/cc. The working temperature of the process is 350o K. The collection
efficiency of the cyclone for a particle diameter of 7 micrometer is
A) 67.75%
B) 77.75%
C) 87.75%
D) 97.75%