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Section 4.2.6. Gas-Solid Separation (Gas Cleaning) PART 1

Total questions: 55

Worksheet time: 28mins

Name
Class
Date
1.

The primary purpose of gas-solid separation in process industries is:

a)

Increase gas density

b)

Remove dust and contaminants from gas streams

c)

Reduce pressure drop

d)

Control temperature of gases

2.

Which gas-cleaning equipment works best for large particles (>50 μm)?

a)

Electrostatic precipitator

b)

Gravity settling chamber

c)

Bag filter

d)

Venturi scrubber

3.

Settling chambers are limited in use because:

a)

They cause high pressure drops

b)

They can only handle coarse dust

c)

They cannot operate at high temperatures

d)

They require electrostatic fields

4.

The separation efficiency of settling chambers depends primarily on:

a)

Particle velocity relative to gas velocity

b)

Bag length

c)

Pressure gradient

d)

Electrical field strength

5.

Which design modification improves the efficiency of settling chambers?

a)

Adding horizontal plates or vertical baffles

b)

Using very high gas velocities

c)

Increasing pressure drop

d)

Using electrostatic wires

6.

Impingement separators rely on:

a)

Particle inertia to strike baffles

b)

Electrostatic charging

c)

Molecular diffusion

d)

Coalescence

7.

Typical particle size removal capability of impingement separators is:

a)

>100 μm

b)

1–2 mm

c)

<0.1 μm

d)

10–20 μm

8.

Compared to settling chambers, impingement separators have:

a)

Lower efficiency

b)

Higher pressure drop

c)

Greater simplicity

d)

Better performance at >50 μm only

9.

Cyclones are the principal gas-solid separators because:

a)

They combine simple construction with moderate efficiency

b)

They use electrostatic charging

c)

They separate gases by diffusion

d)

They require no dust removal

10.

Cyclones are generally suitable for particles:

a)

<0.1 μm

b)

>500 μm

c)

0.5–5 μm

d)

 >5 μm

11.

The most common cyclone design used in industries is:

a)

Straight-through cyclone

b)

Reverse-flow cyclone

c)

Horizontal cyclone

d)

Tangential-only cyclone

12.

In a reverse-flow cyclone, solids are collected:

a)

In the central vertical pipe

b)

At the bottom after sliding down the wall

c)

At the gas exit

d)

At the tangential entry

13.

Which factor increases cyclone collection efficiency?

a)

Lower gas velocity

b)

Higher centrifugal force

c)

Shorter residence time

d)

Larger cyclone diameter

14.

Cyclones can handle:

a)

High temperatures and pressures

b)

Only low-pressure systems

c)

Only low-temperature gases

d)

Corrosive-free streams

15.

Which limitation applies to cyclones?

a)

Cannot separate coarse particles

b)

Struggle with very fine particles <0.5 μm

c)

Require electricity

d)

Only work in batch mode


16.

 Bag filters remove particles by:

a)

Electrostatic charging

b)

 Impingement and precoating of the filter medium

c)

Settling under gravity

d)

Centrifugal force

17.

 Typical efficiency of bag filters is high down to particle size:

a)

100 μm

b)

1 μm

c)

 50 μm

d)

 0.01 μm

18.

Which material is commonly used for bag filter media?

a)

Glass-fiber mats

b)

Steel mesh

c)

Activated carbon

d)

Wooden frames

19.

 Bag filters are cleaned by:

a)

Heating

b)

Vibrating or reverse gas flow

c)

Solvent washing

d)

Centrifugation

20.

 Air filters differ from process filters mainly because:

a)

 They require lower dust collection (<10 mg/m³)

b)

They recover solids

c)

They work only at high pressure

d)

They do not need replacement

21.

 Which type of air filter uses mineral oil to retain dust?

a)

Dry filter

b)

Viscous filter

c)

Continuous filter

d)

Reverse-flow filter

22.

The main limitation of viscous and dry air filters is:

a)

Cannot be replaced

b)

Require periodic cleaning or replacement

c)

 Cannot be scaled up

d)

High pressure drop

23.

Wet scrubbers remove particles mainly by:

a)

Centrifugal force

b)

Countercurrent washing with liquid droplets

c)

Electrostatic attraction

d)

Adsorption


24.

Wet scrubbers are especially advantageous because they can also:

a)

 Neutralize corrosive gases

b)

Recover solvents

c)

 Replace electrostatic precipitators

d)

Remove only coarse particles


25.

Which particle size range can wet scrubbers remove effectively?

a)

<0.1 μm

b)

0.5 μm and above

c)

>100 μm only

d)

>50 μm


26.

Venturi scrubbers increase efficiency by:

a)

Adding plates

b)

Using turbulence to atomize liquid droplets

c)

Settling chambers

d)

Vibrating filters

27.

A cyclone is often combined with a scrubber to:

a)

Neutralize gases and remove agglomerated droplets

b)

Reduce liquid flow

c)

Lower centrifugal force

d)

Eliminate pressure drop

28.

Electrostatic precipitators (ESPs) are most effective for:

a)

Very fine particles

b)

Solvent vapors

c)

Corrosive droplets

29.

Main limitation of ESPs is:

a)

High cost of capital and operation

b)

Poor efficiency

c)

Cannot handle hot gases

d)

No industrial application

30.

Which industry is a major user of electrostatic precipitators?

a)

Textile

b)

Power generation

c)

Pharmaceutical

d)

Food packaging

31.

The principle of ESP operation is:

a)

Centrifugal force separation

b)

Charging particles using high-voltage electrodes

c)

Diffusion

d)

Filtration

32.

In ESPs, high-voltage electrodes are usually:

a)

Wires

b)

Plates

c)

Tubes

d)

Meshes

33.

Collected dust in ESPs is removed by:

a)

Heating

b)

Vibrating or washing electrodes

c)

Cyclone action

d)

Reverse gas flow

34.

Which factor increases ESP efficiency?

a)

High voltage field strength

b)

Low turbulence

c)

High particle density

d)

Low residence time

35.

The primary application of ESPs in power stations is:

a)

Neutralizing corrosive gases

b)

Removal of fine fly ash from coal combustion

c)

Cooling exhaust gases

d)

Increasing gas velocity

36.

Among gas-solid separators, which has the lowest pressure drop?

a)

Gravity settlers

b)

Bag filters

c)

Venturi scrubbers

d)

ESPs

37.

Which method is best suited for handling toxic and corrosive gases with dust?

a)

Wet scrubbers

b)

Bag filters

c)

Settling chambers

d)

Cyclones

38.

Which method would you use to clean air in pharmaceutical cleanrooms?

a)

Air filters

b)

Cyclones

c)

ESPs

d)

Settling chambers

39.

Which separator type is least suitable for removing submicron particles?

a)

ESP

b)

Bag filter

c)

Settling chamber

d)

Wet scrubber

40.

If fly ash particles of ~1 μm must be removed at high efficiency, the best option is:

a)

Cyclone

b)

ESP

c)

Settling chamber

d)

Impingement separator

41.

Which separation method simultaneously cools gases and removes dust?

a)

Scrubber

b)

ESP

c)

Cyclone

d)

Settling chamber

42.

For separation of catalyst attrition dusts (~20 μm), which device is most appropriate?

a)

Settling chamber

b)

Impingement separator

c)

Bag filter

d)

ESP

43.

In designing settling chambers, the required chamber length is estimated using:

a)

Stokes’ law for settling velocity

b)

Reynolds equation

c)

Fanning equation

d)

Antoine’s equation

44.

For maximum cyclone efficiency, the gas should enter:

a)

Radially

b)

Tangentially

c)

Perpendicularly

d)

Axially upward

45.

Bag filters can achieve efficiencies greater than:

a)

50%

b)

80%

c)

99%

d)

70%

46.

Which scrubber type uses turbulence from an orifice for dust capture?

a)

Spray tower

b)

Venturi scrubber

c)

Packed column

d)

Plate tower

47.

The best device for separating coarse fly ash from flue gas is:

a)

Settling chamber

b)

Cyclone

c)

ESP

d)

Bag filter

48.

In ESPs, the grounded electrode is usually designed as:

a)

Plates or tubes

b)

Wires

c)

Fibers

d)

Coated mesh

49.

If the main design priority is low capital cost with moderate dust removal (>10 μm), the equipment of choice is:

a)

Cyclone

b)

ESP

c)

Bag filter

d)

Venturi scrubber

50.

Which separation method is most effective when submicron particles and high efficiency are required despite high costs?

a)

Electrostatic precipitator

b)

Bag filter

c)

Cyclone

d)

Settling chamber

51.

A chemical plant needs to remove dust particles of around 15 μm from hot flue gas. The gas is corrosive. Which gas-cleaning method is most suitable?

a)

Cyclone

b)

Electrostatic precipitator

c)

Settling chamber

d)

Bag filter

52.

A plant has a large volume of low-dust air to clean for a packaging process. Minimal pressure drop is required. The best choice is:

a)

Bag filter

b)

Air filter

c)

Wet scrubber

d)

Cyclone

53.

A gas stream contains coarse catalyst dust (~100 μm). The cheapest, simplest equipment with minimal maintenance is:

a)

Settling chamber

b)

Cyclone

c)

ESP

d)

Wet scrubber

54.

Which of the following is a key advantage of wet scrubbers over dry filtration?

a)

Can remove submicron particles efficiently

b)

Can simultaneously cool and neutralize gases

c)

Has very low capital cost

d)

Requires no liquid supply

55.

A refinery wants to remove water droplets from a hydrocarbon stream. The droplets are finely dispersed, difficult to coalesce. Which equipment is most likely used?

a)

Cyclone

b)

Electrostatic coalescer

c)

Settling chamber

d)

Bag filter