Particulate Pollutants - Air and Noise Pollution - Environmental Science & Engineering Previous Year Questions

1

2024 · Environmental Science & Engineering · Air and Noise Pollution · Particulate Pollutants

Environmental Science & Engineering (ES) 2024

The equipment that can be used to control particulate air pollution in an industrial unit is/are

A

Electrostatic precipitator

B

Cyclone separator

C

Gravity settler

D

Incinerator

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2

2024 · Environmental Science & Engineering · Air and Noise Pollution · Particulate Pollutants

Environmental Science & Engineering (ES) 2024

A gravity settling chamber of height 'H' and length 'L' is designed to control particulate air pollution. In the chamber, the horizontal velocity of air flow is 'V_h' and terminal settling velocity of the target particle is 'V_t' .

Which one of the following expressions is the correct concept used to calculate the minimum size of the target particle that will be removed with 100% efficiency?

A

\(\frac{V_t}{L} = \frac{V_h}{H}\)

B

V_h \times V_t = L \times H

C

V_h = V_t \times L \times H

D

\(\frac{V_t}{H} = \frac{V_h}{L}\)

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3

2024 · Environmental Science & Engineering · Air and Noise Pollution · Particulate Pollutants

Environmental Science & Engineering (ES) 2024

In a cyclone separator of radius 25 cm, a particle is travelling with a gas stream at velocity of 18 m/s. The ratio of centrifugal force to the gravitational force acting on the particle is __________ (rounded off to 2 decimal places).
Consider acceleration due to gravity (g) as 9.8 m/s².

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4

2025 · Environmental Science & Engineering · Air and Noise Pollution · Particulate Pollutants

Environmental Science & Engineering (ES) 2025

A particle dispersoid has 1510 spherical particles of uniform density. An air purifier is proposed to be used to remove these particles. The diameter specific number of particles in the dispersoid, along with the number removal efficiency of the proposed purifier is shown in the following table:

Diameter of the particle (µm)	Number of particles	Number removal efficiency (%)
1	1000	99
10	500	75
100	10	10

The overall mass removal efficiency of the proposed purifier is ______ %. (rounded off to one decimal place)

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5

2021 · Environmental Science & Engineering · Air and Noise Pollution · Particulate Pollutants

Environmental Science & Engineering (ES) 2021

Which of the following is/are the dominant mechanism(s) for the removal of spherical particles with diameter less than 10 μm from a gas stream using a fabric filter?

A

Impaction

B

Gravitation

C

Interception

D

Diffusion

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6

2022 · Environmental Science & Engineering · Air and Noise Pollution · Particulate Pollutants

Environmental Science & Engineering (ES) 2022

PM2.5 concentrations in ambient air can be measured using

A

Beta attenuation method

B

Chemiluminescence method

C

Gravimetric method

D

Non dispersive infrared spectroscopy method

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7

2022 · Environmental Science & Engineering · Air and Noise Pollution · Particulate Pollutants

Environmental Science & Engineering (ES) 2022

A bag filter is used for removal of particulate matter having a range of sizes. The correct sequence of air filtration mechanisms for their removal, in order of decreasing size, is

A

Diffusion, Impaction, Disintegration

B

Disintegration, Impaction, Interception

C

Diffusion, Impaction, Interception

D

Impaction, Interception, Diffusion

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8

2023 · Environmental Science & Engineering · Air and Noise Pollution · Particulate Pollutants

Environmental Science & Engineering (ES) 2023

A boiler in an industry, located where high plume rise is expected, releases flue gas with fine particulate matter. Which one of the following options is most suited and efficient if this particulate matter is intended for reuse?

A

reduce stack height and increase stack diameter

B

use of wet collectors

C

use of flue gas desulfurization (FGD)

D

use of electrostatic precipitator (ESP)

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9

2026 · Environmental Science & Engineering · Air and Noise Pollution · Particulate Pollutants

Environmental Science & Engineering (ES) 2026

In the design of air pollution control devices, size of the particles that are removed with 50% efficiency is termed as ______.

A

mean size

B

mode size

C

cut size

D

median size

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