This set of Air Pollution Control Multiple Choice Questions & Answers (MCQs) focuses on “Control of Gaseous Emissions”.
1. Which of the following two methods are used for capturing gaseous effluents?
a) Sorption and chemical alteration
b) Adsorption and combustion
c) Incineration and absorption
d) Catalytic combustion and incineration
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Explanation: The two methods used for capturing gaseous effluents are sorption and chemical alteration of the gas components. Sorption includes both adsorption and absorption, while chemical alteration includes combustion and catalytic oxidation. The rest of the options list the examples.
2. Which of the following gaseous emission control methods is used frequently in the industry?
a) Catalytic oxidation
b) Incineration
c) Adsorption
d) Absorption
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Explanation: Among the given option, absorption is the most widely used method for the control of gaseous emissions. Combustion (like incineration and catalytic oxidation) is only adopted when the recovered products have no value in the process.
3. What is the driving force in the absorption process?
a) Pressure gradient
b) Concentration gradient
c) Temperature gradient
d) Mass gradient
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Explanation: The concentration gradient is the factor that drives the absorption process. The mass transfer of the pollutant occurs from the gas phase to the liquid phase. This transfer causes a decrease in pollutant concentration in the gas phase.
4. What does the effectiveness of the absorption process depend on?
a) Concentration gradient
b) Pollutant concentration
c) Suitability of scrubbing liquid
d) Partial pressure of the gas
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Explanation: The suitability of the cleaning liquid for the absorption of the particular gas controls the effectivity. One such parameter is that the liquid should dissolve high gas concentrations, for which it should have a high affinity and selectivity.
5. Which of the following is not a property affecting the choice of absorption liquid?
a) Low vapour pressure
b) High gas solubility
c) High selectivity
d) High vapour pressure
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Explanation: The sorption liquid should have a high solubility for the gas to be absorbed. If there is more than one solute in the gas stream, its selectivity towards the gas to be absorbed should be high. Its vapour pressure should be low. Other properties include low viscosity, non-corrosive, non-toxic, et cetera.
6. Which of the following is a suitable solvent for the absorption of sulphur dioxide?
a) Water
b) Magnesium oxide solution
c) Sulphuric acid
d) Ammonia solution
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Explanation: Among the given options, only magnesium oxide solution is suitable for the absorption of sulphur dioxide. Sulphuric acid is suitable for the absorption of ammonia, while ammonia solution and water are used for hydrogen chloride absorption.
7. Which gas is sodium hydroxide not used for the absorption of?
a) Sulphur dioxide
b) Nitrogen oxides
c) Mercaptans
d) Hydrogen sulphide
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Explanation: Sodium hydroxide is a suitable solvent for many gases. It can be used for the absorption of sulphur dioxide, nitrogen dioxide, hydrogen sulphide, chlorine, and phosgene. For mercaptan absorption, sodium hypochlorite is used.
8. Which of the following is not a commonly used absorption unit?
a) Cyclones
b) Packed towers
c) Venturi scrubbers
d) Spray towers
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Explanation: Among the given options, only cyclones are not used for absorption. Cyclones find applications in the separation of particulate matter through physical methods. Packed towers, venturi scrubbers, and spray towers are all commonly used for absorption.
9. What is a limitation of packed towers?
a) Only gases can be separated
b) Very costly
c) Slurries cannot be handled
d) High pressure drops
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Explanation: Packed towers are limited to using only gases and precipitates. Slurries cannot be used in the packed towers because of clogging worries. The packings may get plugged when using thick liquids, which is disadvantageous.
10. Which absorption equipment is most commonly used for the absorption process?
a) Venturi scrubbers
b) Packed towers
c) Tray towers
d) Spray towers
View Answer
Explanation: The most commonly used absorption unit is the packed tower. Packed towers provide continuous contact between the liquid phase and the gas phase, making them highly efficient. The other listed options account for about 10% of the absorption units.
11. In which of the following absorption units do the liquids and the gases flow in the same direction?
a) Tray towers
b) Spray towers
c) Packed towers
d) Venturi scrubbers
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Explanation: Venturi scrubbers have the liquid and the gas moving in the same direction. Tray towers, spray towers, and packed towers utilise the countercurrent flow of the gas and liquid. Here, the liquid and gas flow in opposite directions.
12. Venturi scrubbers are very efficient for the absorption process. What is the reason for not being in high demand?
a) Energy requirement is high
b) Loading capacities are low
c) Because liquid and gas flow in the same direction
d) Low velocity of the gas stream
View Answer
Explanation: Venturi scrubbers are very efficient at gas absorption because of the large interstitial areas accomplished due to the operation mechanism. However, to reach high efficiencies, high gas velocities are required, subsequently having a high energy requirement.
Sanfoundry Global Education & Learning Series – Air Pollution Control.
To practice all areas of Air Pollution Control, here is complete set of 1000+ Multiple Choice Questions and Answers.
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