This set of Air Pollution Control Multiple Choice Questions & Answers (MCQs) focuses on “Selection of Particulate Collectors”.
1. Which of the following is a factor on which the selection of particulate collectors depends?
a) The desired efficiency
b) The collector dimensions
c) The packing load
d) The environmental lapse rate
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Explanation: Among the given options, only desired efficiency of collection affects the choice of the particulate collector. Elements like collector dimensions are affected by the loading capacity. Packing loading only comes into question with the packed bed scrubber.
2. Which of the following is not a factor affecting the selection of the particulate collector?
a) Particle size
b) Concentration of particles in the feed
c) The type of particulates
d) Available space
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Explanation: Except for the particulate type, all the listed factors affect the choice of the collector. Available space and maintenance factors are secondary factors; they come into play when two viable collectors have different utility and space requirements.
3. Once the preliminary selection of the collector is made, what is the next step?
a) Installation
b) Cost analysis
c) Scale-up
d) Testing
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Explanation: The preliminary selection of the particulate collector, is followed by the cost analysis. The cost analysis is done comparatively so that two, or more, devices with similar efficiencies may be analysed. It includes the operating and maintenance cost of the equipment.
4. What is the next step when the general selection of the particulate collector has been performed?
a) Installation
b) Scale-up
c) Testing
d) Operation parameter estimation
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Explanation: Once the general selection has been carried out, the next step is carrying out the actual estimation of operation parameters. These calculations involve the calculation of actual operation efficiency and the pressure drop of the system. Real cost estimates are determined as well.
5. Which of the following particulate types does the medium efficiency cyclone collect with the most efficiency?
a) Coarse dust
b) Fine dust
c) Superfine dust
d) Sticky dust
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Explanation: Coarse dust is collected with the highest efficiency by a medium efficiency cyclone separator. The collection efficiency for coarse dust is approximately 85%. For superfine dust, it is about 25% and about 65% for fine dust.
6. What is the approximate value of efficiency with which a high-efficiency cyclone collects fine dust?
a) 94%
b) 80%
c) 49%
d) 65%
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Explanation: A high-efficiency cyclone collects fine dust with 80% efficiency. Its collection efficiency is about 49% for superfine dust, and 94% for coarse dust. Higher efficiencies of operation are accompanied by higher operating costs.
7. Which particles does the electrostatic precipitator collect with the highest efficiency?
a) Superfine particles
b) Fine particles
c) Coarse particles
d) Sticky particles
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Explanation: Coarse particles have the highest collection efficiencies for the electrostatic precipitator (for other devices as well). It collects coarse particles with 99.5% efficiency, fine particles with 99% efficiency, and superfine particles with 95% efficiency.
8. Among the given options, which particulate collector has the highest collection efficiency for superfine dust?
a) Venturi scrubber
b) High-efficiency cyclone
c) Electrostatic precipitator
d) Irrigated electrostatic precipitator
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Explanation: Among the given options, venturi scrubber has the highest efficiency of collection for superfine dust. The same is true for fine dust and coarse dust. The irrigated electrostatic precipitator comes in second, while the high-efficiency cyclone is the least efficient.
9. Venturi scrubbers have the least efficiency of collection for superfine dust. What is this approximate collection efficiency?
a) 99.8%
b) 99.3%
c) 99.1%
d) 99%
View Answer
Explanation: Venturi scrubbers collect superfine dust with the least efficiency (coarse dust, fine dust and superfine dust). This value of collection efficiency is 99.1%. It collects fine dust with an efficiency of 99.8%. These values are for the medium efficiency venturi scrubber.
10. The high-efficiency electrostatic precipitator has higher collection efficiency, for the collection of coarse particles, than the high energy venturi scrubber.
a) True
b) False
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Explanation: The opposite is true. The high energy venturi scrubber has a higher collection efficiency of (< 99.95%), while the high-efficiency electrostatic precipitator has a lower value (99.5%). In practice, however, these values are equivalent.
11. Before the final selection of particulate collector, which factors are considered?
a) Maintenance factors
b) Cost analysis
c) Environmental factors
d) Operating pressure drop
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Explanation: Before the final selection of the collector, environmental factors are considered, along with the suitability with other equipment in the process. Cost analysis, pressure drop calculations, and maintenance factors are all studied earlier in the selection process.
12. Mechanical collectors are preferred in which of the following industries?
a) Steel industries
b) Paper mills
c) Petroleum refineries
d) Cement industries
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Explanation: Mechanical collectors are efficient at collecting particles of large sizes in processing industries. A huge component gaseous emissions from cement industry is the cement dust, which have large sizes. Other industries like power generation also use mechanical collectors.
13. Which of the following equipment is not used for the collection of particulate matter in the petroleum industry?
a) High-efficiency cyclones
b) Electrostatic precipitator
c) Scrubbing towers
d) Fabric filters
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Explanation: Fabric filters have low utility in the petroleum industries. There is a high chance of the fabric being clogged by sticky particles. Scrubbing towers are quite useful here. Cyclones can handle coarse particles.
14. Which of the following particulate collectors is not preferred for use in the steel industry?
a) Fabric filters
b) Gravity settlers
c) Wet scrubbers
d) Cyclones
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Explanation: Among the given options, gravity settlers are not preferred. Fabric filters, wet scrubbers, and cyclones, as well as electrostatic precipitators are viable for particulate recovery in the steel industry. Smoke, dust and iron oxide are primary particulates released.
15. Which of the following kind of particulate matter is not released from metallurgical operations?
a) Smoke
b) Metal fumes
c) Grease
d) Acid mist
View Answer
Explanation: Except for acid mist, all the listed options are released in the emissions from metallurgical industries. Oil, grease, metal fumes, and smoke removal occurs by collectors like electrostatic precipitators, wet scrubbers, and fabric filters.
Sanfoundry Global Education & Learning Series – Air Pollution Control.
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