NPTEL Course

Air Pollution and Control

Week 10 Assignment 10 (Lecture 46 to 50)

Please select the correct option. All questions contain only one correct answer.

1. Calculate the minimum size of the particle that will be removed with 100 percent efficiency from the gravitational settling chamber under the following conditions:

Air: (i) Horizontal velocity is 1.1 m/s (ii) Temperature is 75⁰C

Particle: (i) Specific gravity = 1.5 (ii) Density of the particle, ���� = 1.5g/cm3 = 1500 kg/m3

Chamber: (i) Length = 15 m (ii) Height = 1.7 m

At 75⁰C viscosity of air is 2.3 x 10-5 kg/m-s. (Take g = 9.81 m/s-2) a. 67.9 µm b. 59.2 µm c. 35.2 µm d. 13.9 µm

Solution:

Given Data:

Horizontal velocity, V = 1.1 m/s

Height, h = 1.7 m

Length, L = 15 m

Viscosity of air, µ = 2.3 x 10-5 kg/m-s

Density of the particle, ���� = 1.5g/cm3 = 1500 kg/m3 a. 5.75 µm b. 8.13 µm c. 10.33 µm d. 12.14 µm

2. A cyclone has an inlet width of 20 cm and five effective turns (N = 5). The gas temperature is 350⁰K, and the inlet velocity is 12 m/s. The average particle density is 1.5 g/cm3. What is the cut diameter (particle size collected with 50% efficiency)? The viscosity of air at 350⁰K is 0.0748 kg/m-h.

Solution: Given data

Inlet width, B = 20 cm

Viscosity of air at 350⁰K , µ =0.0748 kg/m-h

Effective turns, Nt = 5

Inlet velocity, V = 12 m/s average particle density, ρp = 1.5 g/cm

3. A regenerative carbon bed system has three beds in parallel, each having:

• Gas flow rate of 8,500 SCFM (Standard Cubic Feet per Minute)

• Gas temperature of 110°F

• Gas pressure of + 5 inches W.C. (Water Column)

• The barometric pressure is 31.5 inches Mercury (Hg) a. 45.5 ft b. 54.8 ft2 c. 71.8 ft2 d. 93.4 ft2

What is the minimum cross-sectional area of each bed if the gas velocity must be maintained below 120 feet per minute?

Solution:

➢ Given gas characteristics,

• Gas flow rate of 8,500 SCFM (Standard Cubic Feet per Minute)

• Gas temperature of 110°F

• Gas pressure of + 5 inches W.C. (Water Column)

• The barometric pressure is 31.5 inches Mercury (Hg)

• Gas Velocity = 120 ft. per minute

=71.8����

➢ Hence the minimum cross-sectional area of each bed is 71.8 ft2 a. 2.17 lb/hr b. 3.01 lb/hr c. 4.23 lb/hr d. 5.01 lb/hr

4. Calculate the amount of calcium hydroxide (lime) needed to neutralize the HCl absorbed from a gas stream having 45 ppm HCl and a flow rate of 12,000 SCFM. Assume an HCl removal efficiency of 97%.

Solution:

• We know that,

• From above equation, it is clear that 1 mole of lime ����(����)2 is required for the removal of 2 moles of ������

• HCl concentration = 45 ppm = 45 x 10-6 lb-mole HCl

• Flow rate = 12,000 SCFM

• Removal Efficiency = 97%

• The quantity of HCl absorbed in the scrubbing liquid is as follows: •

• Hence the amount of calcium hydroxide (lime) needed to neutralize the HCl absorbed from a gas stream is 3.01 lb/hr.

5. The acceptable threshold level of air pollution in terms of its potential impacts on health and the environment is termed as a. Air quality index b. Air quality standard c. Air quality value d. Air quality threshold a. Sulphur dioxide b. Nitrogen dioxide c. Lead d. Nickel

6. Which of the following pollutants was included in the revised National Ambient Air Quality Standards (NAAQS) of India in 2009.

7. If a person observes a smoke emission using the Ringelmann chart and infers 80% dense smoke, the corresponding Ringelmann number is ___ a. 1 b. 2 c. 3 d. 4 a. Air (Prevention and Control of Air Pollution) Act (Air Act, 1981) b. Environment (Protection) Act (EPA), 1986 c. National Environment Tribunal Act (NETA), 1995 d. National Environment Appellate Authority (NEAA), 1997

8. The _________ act serves as an umbrella act under which various rules and notifications have been framed and issued to take care of the different dimensions of environmental challenge.

9. One of the major government initiatives, GRAP was notified on January 12, 2017, for prevention, control and abatement of air pollution in Delhi and NCR. The GRAP stands for a. Gridded Response Action Plan b. Gridded Response Action Programme c. Graded Response Action Programme d. Graded Response Action Plan

10. National Clean Air Programme (NCAP) targets reduction of 20%–30% of PM2.5 and PM10 concentration by 2024 in comparison to the base year _______ a. 2015 b. 2017 c. 2019 d. 2021