Air Pollution Control Questions and Answers – Gravitational Settling Chambers

This set of Air Pollution Control Multiple Choice Questions & Answers (MCQs) focuses on “Gravitational Settling Chambers”.

1. Which of the following is not false about gravitational chambers?
a) It is used to remove small particles
b) Particles larger than 50 microns cannot be removed
c) It is used to remove particulate matter from emissions
d) It is highly efficient for removing small particles
View Answer

Answer: c
Explanation: Particulates are removed using the gravitational settling chambers. This equipment is used to remove particles with large diameters (greater than 50 microns). It is inefficient at removing small particles.

2. Which types of particles are removed from gas streams using gravitational settlers?
a) Small and smooth
b) Small and coarse
c) Large and smooth
d) Large and coarse
View Answer

Answer: d
Explanation: Gravitational chambers are ideal for removing large and coarse particles from the gaseous effluent stream. Large particles are capable of settling under gravity, unlike small particles (sizes less than 50 microns) that remain suspended.

3. Gravitational settling chambers experience which of the following conditions?
a) High pressure drop
b) Low pressure drop
c) High-speed settling
d) High operating costs
View Answer

Answer: b
Explanation: These collectors offer low pressure drops and low maintenance because of their simplicity. Even though such advantages exist, these settlers have low efficiencies for small particle collection, which reduces their utility.

4. Which of the following is an advantage of using gravitational settlers?
a) Low maintenance
b) Low efficiency of collection for small particles
c) High pressure drop
d) Prone to breakdown
View Answer

Answer: a
Explanation: Gravitational settling chambers are highly advantageous because of their low maintenance requirements and low pressure drops. However, they have low efficiencies when it comes to the collection of small particles. This disadvantage makes them unviable.

5. Which of the following is a disadvantage of gravitational settlers?
a) Low efficiency
b) High pressure drop
c) High maintenance
d) Short life
View Answer

Answer: a
Explanation: This equipment is not considered a viable choice because of its low efficiency. Most particulates have sizes smaller than 50 microns, for which gravitational settlers have low collection efficiency.

6. Particles of which sizes can be collected efficiently by gravity settlers?
a) > 50 microns
b) < 50 microns
c) < 25 microns
d) > 25 microns
View Answer

Answer: b
Explanation: Gravity settlers can efficiently collect particles of sizes larger than 50 micrometres. Particles of such diameters can readily settle under the influence of gravity, which is not the case for particles lesser than 50 microns.

7. Why do gravity chambers have low utility?
a) High maintenance
b) High pressure drops
c) Most particles are smaller than they can collect
d) High-velocity operation
View Answer

Answer: c
Explanation: In the industries, particulates are usually smaller than 50 microns. Gravity settlers have low collection efficiencies for particles of such sizes. This limitation primarily reduces its utility. The opposite of the listed options is true for this device.

8. At which conditions does the gravity chamber operates?
a) High pressure drops
b) High operating costs
c) High gas velocities
d) Low gas velocities
View Answer

Answer: d
Explanation: In gravitational settlers, the particulate containing gas is allowed to flow at low velocities for adequate time periods. These conditions permit the particles to settle due to the action of gravity.

9. How does the Howard type gravity settlers allow for higher collection efficiencies?
a) Lower settling velocity
b) Higher settling velocity
c) Lower fall distance
d) Higher fall distance
View Answer

Answer: c
Explanation: In this modification of the settling chamber, improved efficiencies are observed. The settling velocities of the conventional and modified settlers remains the same, but the fall distance is much shorter.

10. Which operating condition remains the same between the conventional and Howard settling chambers?
a) Fall distance
b) Settling velocities
c) Pressure drop
d) Loading capacity
View Answer

Answer: b
Explanation: The settling velocities remain identical across the two types of settling chambers. The particle fall distance is shorter for the Howard type settler, because of the presence of multiple settling trays (as opposed to one chamber, as in the case of the conventional settler); this makes its efficiency higher.

Sanfoundry Global Education & Learning Series – Air Pollution Control.

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Manish Bhojasia - Founder & CTO at Sanfoundry
Manish Bhojasia, a technology veteran with 20+ years @ Cisco & Wipro, is Founder and CTO at Sanfoundry. He lives in Bangalore, and focuses on development of Linux Kernel, SAN Technologies, Advanced C, Data Structures & Alogrithms. Stay connected with him at LinkedIn.

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