This set of Air Pollution Control Multiple Choice Questions & Answers (MCQs) focuses on “Control of Gaseous Emissions – Set 3”.
1. When is the combustion of gases employed in the industry?
a) When the gas has no recovery value
b) When the loading capacity is too low
c) For energy production
d) For waste disposal
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Explanation: Combustion is chosen as the gaseous waste disposal method when the recovered gases have no added value. This drawback makes adsorption and absorption unfeasible economically. An added bonus of combustion is energy recovery.
2. When is incineration chosen as the combustion method?
a) When energy recovery is needed
b) When sufficient combustible materials are present in the gas stream
c) When hazardous materials are present in the gas stream
d) When other combustion methods are not viable
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Explanation: Incineration is chosen when the gas stream contains sufficient combustible materials. If materials are insufficient, then other combustion methods are applied. Care should be taken of the combustion products, though, as they might pose pollution problems of their own.
3. Which of the following is not necessary for complete combustion?
a) Contact between oxygen and combustible materials
b) Turbulence
c) Capacity of the gas to be incinerated
d) Residence time
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Explanation: Of the given options, only the gas capacity does not affect the completeness of combustion. The complete contact between combustible materials and oxygen is necessary for complete combustion.
4. What are the three T’s of combustion?
a) Time, Turbulence, and Temperature
b) Temperature, Toxicity and Tolerance limit
c) Temperature, Time and Tolerance limit
d) Time, Turbulence and Toxicity
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Explanation: Temperature, time and turbulence are the three T’s of combustion. Turbulence ensures the thorough mixing of the pollutants and air. Residence time has to be sufficient enough to ensure thorough mixing and burning.
5. Which of the following is not one of the three usual modes of combustion of air pollutants?
a) Incomplete combustion
b) Catalytic oxidation
c) Flaring
d) Thermal incineration
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Explanation: Of the given methods, only incomplete combustion is not incorporated in the combustion process. Flaring is also known as direct combustion. Highly combustible substances that have high heating values are flared.
6. When is the flaring of gaseous pollutants not conducted?
a) When there is no particulate matter
b) When it contains a high amount of inorganic pollutants
c) When very high temperatures are required
d) When a high quantity of moisture is present
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Explanation: Flaring is not conducted when a large quantity of inorganic pollutants are present in the gas stream. Combustion of inorganic waste (like sulphur, chlorine) releases air pollutants of these materials, hence, pollution problems of their own.
7. What is the key operating cost of using incinerators?
a) The catalysts
b) Installation
c) Fuel
d) Incineration operation
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Explanation: The key operating costs are fuel, which sustains the temperature levels of incineration. The temperatures that need to be maintained in incinerators range from 500 degrees Celsius to 800 degrees Celsius. No catalysts are used in its operation.
8. When is catalytic oxidation of air pollutants carried out?
a) When thermal incineration is not feasible
b) When absorption is not feasible
c) When the particulate matter is present
d) When large amounts of pollutants are present
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Explanation: Catalytic oxidation of air pollutants should be done when thermal incineration becomes very expensive. An advantage of incineration is heat recovery, and when that is not significant, this method is chosen.
9. What are the catalysts in the catalytic oxidation process made of?
a) Activated carbon
b) Platinum
c) Benzene
d) Carbon tetrachloride
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Explanation: Benzene and carbon tetrachloride are organic solvents. Activated carbon is an adsorbent. Precious metals are used as catalysts; these include platinum and its alloys, palladium and its alloys, et cetera.
10. For catalytic oxidation, what should the gas stream be free of?
a) Gases
b) Moisture
c) Solid particulates
d) Liquid aerosols
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Explanation: The gas stream should be free of solid particulates. This condition should be especially satisfied with metals. Such substances can poison the catalysts, which may slow down or stop the process altogether.
11. Which materials cause smoke problems in the combustion process?
a) Sulphur
b) Chlorine
c) Inorganic solvents
d) High molecular weight hydrocarbons
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Explanation: Sulphur and chlorine, if present in the gas stream, convert into their oxides during combustion. High molecular weight hydrocarbons, like aromatics, create smoke problems, which are disadvantageous to combustion.
12. Destruction of which of the following is not a complete combustion application?
a) Chlorine compounds
b) Odours
c) Reactive materials
d) Reduction of oxidised pollutants
View Answer
Explanation: The products of complete combustion are carbon dioxide and moisture. If incomplete combustion takes place, products like chlorine compounds are formed, not destroyed. The thorough breakdown of odours, reactive materials, and oxidised materials occurs during complete combustion.
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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