This set of Air Pollution Control Multiple Choice Questions & Answers (MCQs) focuses on “Gaseous Pollutants – Control of Sulphur Dioxide Emissions – Set 2”.
1. Which of the following is not a disadvantage of using fluidized bed combustion units?
a) Increased formation of nitrogen oxides
b) Installing additional units for limestone preparation
c) Regeneration of calcium sulphate
d) Different boiler design
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Explanation: Fluidized bed combustion units produce lower quantities of nitrogen oxides, which is advantageous. This statement is opposite to the given option, and therefore, that is false. The other listed options are all drawbacks of using fluidized beds.
2. Why is wet scrubbing not preferred for desulphurization of flue gases?
a) Uneconomic
b) Ineffective
c) Hot plumes are released
d) Adds more steps to the process
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Explanation: Cold plumes are released when wet scrubbing is used, which is disadvantageous. Additionally, the process is uneconomic and is problematic to implement in existing plants. However, the process itself is very effective.
3. Why is the flue gas reheated when wet scrubbing is used to remove sulphur compounds?
a) Removes more sulphur content
b) Expand gas
c) Plume is cold
d) Kills bacteria
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Explanation: Cold plumes are not preferred because they reduce the buoyancy of the plume. This result may cause an increase in ground-level pollution. To avoid this phenomenon, the desulphurized plume is reheated.
4. Which of the following is not a method used to desulphurize stationary combustion sources?
a) Treatment of flue gases
b) Desulphurise during combustion
c) Extraction from fuels
d) Emission from high stacks
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Explanation: Among the given options, “emission from high stacks” is not a treatment method. Though the pollutant may disperse in the atmosphere, it still contributes to air pollution. Either desulphurization is done pre-combustion, during combustion, or post-combustion.
5. Which method is used for the dry removal of sulphur oxides from flue gases?
a) Adsorption
b) Cyclones
c) Incineration
d) Tray towers
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Explanation: The method is adsorption. Cyclones remove particulate matter. Tray towers, which are a method of absorption, are not used for dry desulphurization of flue gases. Incineration is adopted only when recovery produces no valuable products.
6. Which of the following adsorbents are popularly used for the desulphurization of flue gases?
a) Molecular sieves
b) Activated carbon
c) Silica gel
d) Alumina
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Explanation: Among the given options, only activated carbon is used to remove sulphur oxides from flue gases. Other adsorbents used for this process are metal oxides, particularly aluminium sodium oxide (alkalized alumina).
7. Which of the following metal oxides is used to remove the sulphur oxides from flue gases?
a) Manganese oxide
b) Activated carbon
c) Magnesium oxide
d) Calcium oxide
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Explanation: Among the given options, only magnesium oxide is preferred as an adsorbent. Activated carbon is not a metal oxide. Other metal oxides include alkalized alumina. Additionally, copper and cobalt oxides are also suitable adsorbents.
8. How much sulphur dioxide is recovered using manganese oxide as the adsorbent?
a) 80%
b) 95%
c) 90%
d) 85%
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Explanation: Using manganese oxide for the dry removal of sulphur dioxide from flue gases is very advantageous. Removal from this process is about 90%. However, this value is limited to one kind of process using manganese oxide only.
9. What is a limitation of using alkalised alumina for the removal of sulphur oxides from flue gases?
a) Expensive
b) Maintenance of sorption strength
c) High-temperature operation
d) Complicated
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Explanation: The main drawback of the process is the maintenance of the adsorption strength of the adsorber. Additionally, continuous operation and regeneration causes the breakdown of the process and makes it uneconomical.
10. What is the advantage of using activated carbon as an adsorbent for removing sulphur dioxide from flue gases?
a) Space requirement is low
b) High-temperature operation
c) High surface area of the adsorbent
d) Regeneration is easy
View Answer
Explanation: The use of activated carbon is advantageous. It is so because the activated carbon has a high surface area and is inexpensive. The operation itself takes place at relatively low temperatures. Regeneration is not particularly easy since it is done at high temperatures.
Sanfoundry Global Education & Learning Series – Air Pollution Control.
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