# Energy Engineering Questions and Answers – Mechanical Dust Collectors

This set of Energy Engineering Multiple Choice Questions & Answers (MCQs) focuses on “Mechanical Dust Collectors”.

1. Gravitational separator works on the principle of __________
a) Size of particulate
b) Shape of particulate
c) Weight of particulate
d) Color of the particulate

Explanation: Gravitational separation is an industrial method of separating two components, either a suspension, or dry granular mixture where separating the components with gravity is sufficiently practical, i.e. the components of the mixture have different specific weights.

2. What is the use of baffles in the gravitational separators?
a) To separate types of dust
b) To settle the dust by letting them to strike
c) To control the flow of dust particles
d) To blow the dust

Explanation: Baffles are placed in the direction of flow of flue gases. The dust particle strike down and settle. Heavier dust particles settle at the bottom by striking on to the baffles and lighter dust particles are exhaust into atmosphere.

3. What is the most effective advantage of gravitational separators?
a) They consume no power
b) They just need small amount of space for operation
c) They are cost effective
d) Time taken for operation is very less

Explanation: The most notable advantage of the gravitational separators is their cost effectiveness. Gravity separation is an attractive unit operation as it generally has low capital and operating costs, uses few if any chemicals that might cause environmental concerns.

4. Which principle does cyclone separator use?
a) Gravitational force
b) Vortex velocity
c) Inertia
d) Temperatures of air

Explanation: Cyclone separators or simply cyclones work on the principle of inertia to move particulate matter from flue gases. In these high velocity dusts carrying gas is made to pass through conical separator in tangential direction. This results in centrifugal action, throwing away the heavier dust particles to the sides of conical chamber.

5. Cyclone separators are also known as __________
a) Twist cleaners
b) Squall
c) Pre-cleaners
d) Zephyr cleaners

Explanation: Cyclone separators are a part of a group of air pollution control devices known as pre-cleaners as they generally used to roughly remove large pieces of particulate matter. This prevents finer filtration methods from having to deal with large, more abrasive particles later on.
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6. What is called when several cyclone separators are operated parallely?
a) Octa-cyclone
b) Multi-cyclone
c) Center-cyclone
d) Para-cyclone

Explanation: When several cyclone operators are operated parallely, when this system is setup it is called multi-cyclone. It is important to note that cyclones can vary drastically in their size. The size of the cyclone depends largely on how much flue gas must be filtered, and thus larger operations tend to need larger cyclones.

7. What is the range of particulate removing efficiency of cyclone separators?
a) 50-99%
b) 20-80%
c) 70-90%
d) 70-95%

Explanation: Cyclone separators are generally able to remove somewhere in the range of 50-99% of all particulate matter. How well the cyclone separators are actually able to remove this matter depends largely on particle size. If there is large amount of lighter particulate matter, less of these particles are able to be separated out. Because of this, cyclone separators work best on flue gases that contain large amounts of big particulate matter.

8. What is Baghouse?
a) Filters arranged in parallel form
b) Filters arranged throughout the system
c) Filters arranged randomly
d) Filters arranged alternatively

Explanation: A fabric filter element made up of a long hollow cylindrical tube, that provides a large surface per unit of gas volumetric flow rate is called as baghouse filter and a system consisting of large number of such filter elements arranged in parallel rows is called a baghouse.

9. What is the work of the baghouse filter?
a) To remove the hot air from furnace
b) To separate the solid particles from dust produced
c) To remove dust particles from flue gas
d) To wash away the contamination of dust on the walls of furnace

Explanation: Baghouse filters are used to remove dust particles from the flue gas produced from the combustion in boiler. These are also called as fabric filters or fabric dust collectors, designed to use fabric filter tubes, envelopes or cartridges to capture or separate dust and particulate matter when the gas is made to pass through the voids.

10. What is the use of wet scrubber in the dust collection?
a) Remove flue gas
b) Remove Scales on the furnace surface
c) Remove the dust that has the moisture content
d) Remove pollutants

Explanation: Wet scrubber is used remove the pollutants. The polluted gas stream is brought into contact with the scrubbing liquid, by spraying it with the liquid, by a pool of liquid, or by some other contact method, so as to remove the pollutants.

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