Untitled Quiz

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Questions and Answers

How is air pollution defined?

Air pollution is defined as the presence of one or more contaminants in the air in such quantities and for such durations which may be or tend to be injurious to human, animal or plant life, or property, or which unreasonably interferes with the comfortable usage of air.

What are the main causes of air pollution?

The main cause of air pollution is combustion.

What are the three broad categories of air pollutants?

Primary pollutants, Secondary pollutants, Tertiary pollutants
Natural contaminants, Aerosols, Gases and Vapors (correct)
Particulates, Gases and Vapors, Solid Wastes

What is a primary pollutant?

A pollutant emitted directly from a source (A) Signup and view all the answers

The impact of particulate matter on human health depends on its size, shape, and composition.

True (A) Signup and view all the answers

What are the four main types of particulate emission control by mechanical separation?

Gravitational settling chambers, Cyclone separators, Fabric filters, Electrostatic precipitator (A) Signup and view all the answers

Which type of air pollution control method involves removing particulate matter from gas streams by incorporating the particles into liquid droplets directly on contact?

Wet gas scrubbing Signup and view all the answers

What is the most widely used device for controlling particulate emission at industrial installations?

Electrostatic precipitator Signup and view all the answers

Which of the following is NOT an advantage of using an electrostatic precipitator?

High initial cost (A) Signup and view all the answers

The efficiency of an electrostatic precipitator is primarily influenced by the size of the unit and the amount of independent electrical energization.

True (A) Signup and view all the answers

What is the primary purpose of controling emissions from industrial sources?

The threefold purpose of controlling emissions from industrial sources is the recovery of the valuable materials for economic benefit, the removal of abrasive dusts to reduce wear on fan components, and the removal of undesirable substances from gases before they are discharged into the atmosphere. Signup and view all the answers

What are the four distinct phases of the electrostatic precipitator process?

Ionization or corona generation, Charging of particles, Migration and precipitation of particles, Removal of deposited dust (B) Signup and view all the answers

What are the two types of corona discharge?

The two types of corona discharge are negative corona and positive corona. Signup and view all the answers

Why is negative corona preferred for industrial applications while positive corona is used for cleaning air in inhabited spaces?

The common use of negative corona in industrial applications is due to its effectiveness in capturing and removing particulates. However, the production of ozone in negative corona makes it unsuitable for air cleaning in inhabited spaces. In inhabited spaces, positive corona is used because it does not produce ozone. Signup and view all the answers

What is the process called where collected particles are removed from the collecting surface?

The process of removing collected particles from the collecting surface is called rapping or shaking. Signup and view all the answers

Which of the following is NOT a type of electrostatic precipitator?

Cone-Wire Precipitator (A) Signup and view all the answers

Two-stage electrostatic precipitators are typically more efficient than single-stage precipitators for smaller particles.

True (A) Signup and view all the answers

The efficiency of a fabric filter is primarily determined by its pressure drop and air-to-cloth ratio.

True (A) Signup and view all the answers

What are the three common types of baghouses based on their cleaning method?

The three common types of baghouses based on their cleaning method are reverse-air, shaker and pulse-jet. Signup and view all the answers

What is the primary function of a fabric filter in the overall process of particulate removal?

Provide structural support (A) Signup and view all the answers

In which type of adsorption process is the contaminant weakly held to the solid surface?

Physical Adsorption Signup and view all the answers

When is chemical adsorption used?

Chemical adsorption is frequently used in situations that require a strong binding between the contaminant and the solid surface, such as for the control of acid gases and mercury vapor. Signup and view all the answers

What is the main difference between physical and chemical adsorption?

The key difference between physical and chemical adsorption lies in the manner in which the gas molecule is bonded to the adsorbent. In physical adsorption, weak intermolecular forces are responsible for the bonding, while in chemical adsorption, a chemical reaction occurs, resulting in a stronger bond. Signup and view all the answers

Adsorption processes typically operate at efficiencies of 90% to 98% over long time periods.

True (A) Signup and view all the answers

Which of the following is NOT a factor affecting the performance of an adsorption system?

Surface Area (A) Signup and view all the answers

What is the primary method for regenerating an adsorbent bed?

The primary method for regenerating an adsorbent bed is thermal swing, where the bed is heated to reduce the adsorption capacity, and then cooled for subsequent use. Signup and view all the answers

What are the four main categories of adsorption regeneration methods?

The four main categories of adsorbent regeneration are thermal swing, pressure swing, inert purge gas stripping and displacement cycles. Signup and view all the answers

In general, lower gas velocities through an adsorbent bed result in higher capture efficiency.

True (A) Signup and view all the answers

What are the four key factors to consider in the design of an absorption tower?

The four key factors to consider in the design of an absorption tower are providing a large interfacial contact area, ensuring good mixing between gas and liquid phases, allowing sufficient residence time for the phases, and ensuring a high degree of solubility of the contaminant in the absorbent. Signup and view all the answers

Which of these is NOT a type of absorption tower?

Cyclone tower (A) Signup and view all the answers

What are the three steps involved in the absorption process?

The three steps involved in the absorption process are: diffusion of the pollutant from the bulk gas phase to the gas-liquid interface, transfer of the gaseous pollutant across the interface to the liquid phase, and diffusion of the pollutant in the bulk area of the liquid. Signup and view all the answers

What is the defining characteristic of a cyclone separator?

Cyclone separators are designed to use centrifugal forces to separate particles. Signup and view all the answers

Larger-diameter cyclones are known to have better collection efficiencies for particles between 40 and 50 µm.

True (A) Signup and view all the answers

Cyclones are highly efficient in removing very small particles.

False (B) Signup and view all the answers

What is the primary factor that determines the collection efficiency of a cyclone?

The collection efficiency of a cyclone is primarily determined by the centrifugal force, directly affected by factors such as the gas velocity and the size of the cyclone. Signup and view all the answers

What is the formula for calculating the centrifugal force (Fc) in a cyclone?

$Fc = (mv^2)/r $ (D) Signup and view all the answers

The separation factor in a cyclone is directly proportional to the square of the tangential velocity and inversely proportional to the gravitational acceleration.

True (A) Signup and view all the answers

What are the key design parameters in a bag house filter?

The key design parameters in a bag house are pressure drop and air-to-cloth ratio. Signup and view all the answers

Flashcards

Air Pollution

Presence of harmful contaminants in the air, in quantities that can be dangerous to life forms, property, or hinder comfort.

Air Quality

The condition of the air, determined by the amount and type of pollutants present.