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ChELE > Particle Technology > Flashcards

Particle Technology Flashcards

1
Q

this refers to the treatment of material containing a natural amount of moisture or a material that has been dry before screening

Wet Screening
Dry Screening

A

Dry Screenin

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2
Q

This refers to an operation where water is added to the material being treated for the purpose of washing, and facilitating the passage of the find material through the screen

Wet Screening
Dry Screening

A

Wet Screening

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3
Q

this is a unit operation, where a mixture of various sizes of particles is separated into two or more portions, each of which is more uniform in particle size than the original mixture

a. Filtration
b. Screening
c. Sedimentation
d. nota

A

Screening

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4
Q

THREE TYPES of testing sieves

A

Tyler Standard Sieve Series
US Sieve Series
International Test Sieve series

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5
Q

this type of screen is most widely used where large capacity and high-efficiency are desired.

a. Reciprocating Screens
b. Vibrating Screens
c. Tumbling Screen
d. sifter

A

b.

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6
Q

This type of screen is good for accurate sizing of large lumps

a. Reciprocating Screens
b. Vibrating Screens
c. Tumbling Screen
d. sifter

A

a.
Reciprocating Screen
- for handling fine separations
- usually dry, light, or bulky materials, light metal powders, powdered foods and granular materials

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7
Q

This type of screen can provide very good separation of fine products

a. Reciprocating Screens
b. Vibrating Screens
c. Tumbling Screen
d. sifter

A

c.

• Tumbling screen is also called a wobble

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8
Q

This type of screen is used to remove lumps from powder or granular materials

a. Probability screens
b. Paddle driven screens
c. Revolving screen
d. sifter

A

b

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9
Q

these type of screens are useful in the chemical in fertilizer industry

a. Reciprocating Screens
b. Vibrating Screens
c. Tumbling Screen
d. sifter

A

b

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10
Q

this type of screen is characterized by low speed oscillations (300-400 rpm)

a. Reciprocating Screens
b. Vibrating Screens
c. Oscillating screen
d. Grizzlies

A

c

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11
Q

The minimum clear space between the edges of the opening in the screening surface and is usually given in inches or millimeters.

a. sieve
c. mesh number
b. aperture
d. holes

A

b

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12
Q

The screen used in making size separation smaller than 4-mesh and larger than 48- mesh.

a. grizzly screen
b. gyratory screen
c. oscillating screen
d. vibrating screen

A

d

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13
Q

Box-like machines, either round or square with a series of screen clothes nested atop one another.

a. reciprocating screen
b. oscillating screen
c. electricity vibrated screen
d. gyratory screen

A

d

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14
Q

The removal of a small amount of oversize from a feed which is called

a. scalping
b. desliming
c. coarse separation
d. dewatering

A

a

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15
Q

Removal of free water from a solids-water mixture and is generally limited to 4 mesh and above.

a. scalping
b. dewatering
c. trash removal
d. separation

A

b

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16
Q

Making a size separation smaller than 48-mesh is called

a. coarse separation
c. ultrafine separation
b. fine separation
d. scalping

A

c

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17
Q

Another name for revolving screen is

a. shaking screen
b. vibrating screen
c. mechanically vibrated screen
d. trommel screen

A

d

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18
Q

The mesh number of a screen denotes

a. the area of the screen in square inch
b. the number of openings per linear inch of screen
c. the number of layers in a screen system
d. the number of screens needed to obtain the required fines

A

b

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19
Q

The Tyler Standard screen series is characterized by

a. square root of two ratio of areas between successive screens
b. square root of four ratio of linear openings between successive screens
c. twice the area ratio between successive screens
d. none of these

A

c

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20
Q

The ratio of the clear opening corresponding to a mesh size in the Tyler Standard reen series to that of the next smaller screen is

a. 2
b. sqrt 2
c. 1.5
d. none of these

A

b

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21
Q

The ratio of the area of the opening in one screen (Tyler Series) to the opening of the next smaller screen is

a. 1.5
c. 12
b. 1
d. none of these

A

d

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22
Q

Increasing the capacity of a screen

a. decreases the screen effectiveness
b. increases the screen effectiveness
c. does not affect the screen effectiveness
d. none of these

A

a

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23
Q

The screen efficiency is

a. recovery + rejection
b. recovery
c. rejection
d. none of these

A

d

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24
Q

As the particle size is reduced

a. screening becomes progressively more difficult
b. screening becomes progressively easier
c. capacity and effectiveness of the screen is increased
d. none of these

A

a

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25
Q

A screen is said to be blinded when

a. oversize are present in undersize fraction
b. undersize are retained in oversize fraction
c. the screen is plugged with solid particles
d. its capacity is abruptly increased

A

c

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26
Q

Size measurement of ultrafine particles can be best expressed in terms of

a. centimeter
c. micron
b. screen size
d. surface area per unit mass

A

d

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27
Q

Trommels separate a mixture of particles depending on their

a. size
c. screen size
b. wettability
d. electrical and magazine

A

a

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28
Q

Screen capacity is expressed in terms of

a. tons/h
b. tons/ft^2
c. both a and b
d. tons/h-ft^2

A

d

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29
Q

The hardness of the material is measured by the ______ scale

A

Mohs scale

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30
Q

Gyratory crusher power consumption is ________ than Jaw crushers.

Higher or lower

A

lower

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31
Q

Accdg to Taggart’s rule, if T/S^2<1.115,
use ________.

Jaw crusher or Gyratory Crusher

A

Jaw crusher

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32
Q

Accdg to Taggart’s rule, if T/S^2>1.115,
use ________.

Jaw crusher or Gyratory Crusher

A

Gyratory crusher

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33
Q

This machine is widely used in the clay industry

a. Gyratory
b. Edge runners
c. Crushing Rolles
d. Ball mills

A

Edge runners

34
Q

The term applied to all ways in which particles of solids are cut or broken into smaller pieces

a. size reduction
b. screening
c. comminution
d. crushing

A

a

35
Q

The hardness of a mineral is a criterion of its resistance to crushing. Which of the following is an example of a hard material?

a. talc
b. calcite
c. sapphire
d. feldspar

A

c

36
Q

States that the energy required for crushing is proportional to the new surface created.

a. Rittinger’s Law
b. Kick’s Law
c. Bond Law
d. Energy Law

A

a

37
Q

It is defined as the efficiency of technical grinding compared with that of laboratory crushing experiments.

a. Grinding Efficiency
b. Bond Work Index
c. Practical Energy Efficiency
d. none of these

A

c

38
Q

In comminution, the energy requirement is determined theoretically by

a. the initial and final sizes of the particles
b. the type of equipment
c. the change in shape of the particle
d. none of these

A

a

39
Q

Size reduction is important in chemical engineering since

a. it prevents chemical engineers from becoming overweight
b. it makes products to become uniform in size
c. it prepares raw materials of the desired sizes prior to processing
d. none of these

A

c

40
Q

Equivalent diameter of a particle is the diameter of the sphere having the same

a. ratio of surface to volume as the actual volume
b. ratio of volume to surface as the particle
c. volume as the particle
d. none of these

A

a

41
Q

For coarse reduction of hard solids, use
a. impact
b. attrition
c. compression
d. cutting

A

c

42
Q

Soft and non-abrasive materials can be made into fines by

a. attrition
c. cutting
b. compression
d. none of these

A

a

43
Q

Crushing efficiency is the ratio of
a. surface energy created by the crushing to the energy absorbed by the solid
b. energy absorbed by the solid to that fed to the machine
c. energy fed to the machine to the surface energy created by the crushing
d. energy absorbed by the solid to the surface energy created by the crushing

A

a

44
Q

Bond Crushing Law

a. calls for relatively less energy for the smaller product particle than does the
Rittinger Law
b. less realistic in estimating the power requirements of commercial crushes
c. states that the work required to form particle of any size from very large feed is proportional to the square root of the volume to surface ratio of the product
d. states that the work required for the crushing is proportion

A

a

45
Q

Work index is defined as the

a. gross energy (kWh/ton of feed) needed to reduce very large feed to such a size that 80% of the product passes a 100 micron screen
b. energy needed to crush one ton of feed to 200 microns
c. energy (kWh/ton of feed) needed to crush small feed to such a size that 80% of product passes a 200-mesh screen
d. energy needed to crush one ton of feed to 100 microns

A

a

46
Q

The operating speed of a ball mill should be
a. less than the critical speed
b. much more than the critical speed
c. at least equal to the critical speed
d. none of these

A

a

47
Q

fluid energy mill is used for
a. cutting
b. grinding
c. ultragrinding
d. crushing

A

c

48
Q

Wet grinding in a revolving mill

a. gives less wear on chamber walls than dry grinding
b. requires more energy than for dry grinding
c. increases capacity compared to dry grinding
d. complicates handling of the product compared to dry grinding

A

c

49
Q

Cement clinker is commonly reduced to fine size using a

a. Roll Crusher
b. Ball Mill
c. Tube Mill
d. Hammer Mill

A

c

50
Q

If the motion of a particle is impeded by other particles, which will happen when the particles are near each other even though they are not actually colliding, the process is called

a. free settling
b. unhindered settling
c. gravity settling
d. hindered settling

A

d

51
Q

The drag coefficient in hindered settling is __________ compared to free settling.

a. greater than
b. less than
c. constant
d. varying

A

a

52
Q

The operation by which solids are separated from liquids due to difference in their respective densities is

a. screening
b. adsorption
c. sedimentation
d. absorption

A

c

53
Q

The separation of solid particles into several size fractions based upon the settling velocities in a medium is called

a. settling
c. flotation
b. filtration
d. classification

A

d

54
Q

Device in which a current of air separates particles with different sedimentation velocities.

a. agitator
b. air elutriator
c. classifier
d. air conveyor

A

b

55
Q

The constant velocity with which a body moves relative to the surrounding fluid when the forces acting on it (gravitational or centrifugal or electrostatic forces) are equal to the friction force acting against the motion.

a. terminal velocity
c. maximum velocity
b. settling velocity
d. all of these

A

a

At this point the object stops accelerating and continues falling at a constant speed called the terminal velocity (also called settling velocity).

It occurs when the sum of the drag force (Fd) and the buoyancy is equal to the downward force of gravity (FG) acting on the object.

56
Q

An apparatus in which particles settle in a liquid by gravitational or centrifi and are removed as a concentrated slurry.

a. classifier
b. thickener
c. elutriator
d. agitator

A

b

57
Q

Drag is defined as the force exerted by

a. the fluid on the solid in a direction opposite to the motion of the solid
b. the fluid on the solid in the direction of motion of the solid
c. the solid on the fluid
d. none of these

A

a

58
Q

Drag coefficient for flow past an immersed body is the ratio of

a. shear stress to the product of velocity head and density
b. shear force to the product of velocity head and density
c. average drag per unit projected area to the product of the velocity head and density
d. none of these

A

c

59
Q

At low Reynolds Number

a. viscous forces are unimportant
b. viscous forces equal the inertial forces
c. viscous forces control and inertial forces are unimportant
d. gravity forces control

A

c

low Re = Laminar = high viscosity

• Inertial force: The main cause of fluid movement that resists a change in velocity of an object. The force that keeps fluid moving against viscous [ viscosity] forces
• Viscous forces: Resistance to flow

If Finertial&raquo_space; Fviscous → Turbulent Flow; else Laminar Flow

60
Q

At high Reynolds Number

a. inertial forces control and viscous forces are unimportant
b. viscous forces predominate
c. inertial forces are unimportant and viscous forces control
d. none of these

A

a

high Re = Turbulent = low viscosity

61
Q

The ratio of drag force per unit area to the product of fluid density and the velocity head is called

a. buoyant coefficient
b. drag coefficient
c. friction factor
d. shear coefficient

A

b

62
Q

In order for a particle to move through a fluid under the influence of gravity, there must be

a. velocity difference
b. pressure difference
c. density difference
d. temperature difference

A

c

63
Q

In continuous thickeners, separation of solid particles can be achieved if the settling velocity of the solids is ________
compared to the velocity of the displaced liquid

a. equal
b. less
c. greater
d. none of these

A

c

64
Q

is the upward force exerted on an object wholly or partly immersed in a fluid.

a. external force
b. gravitational
c. buoyant
d. drag

A

c

• buoyant force is the upward force a fluid exerts on an object.
• Archimedes’ Principle is the fact that buoyant force is equal to the weight of the displaced fluid.

65
Q

is defined as the force which resists the motion of a body with fluid.

a. external force
b. gravitational
c. buoyant
d. drag

A

d

ex: air resistance

66
Q

Buoyant force

a. for non symmetrical bodies is not vertical
b. depends on the depth of the submergence of the floating body
c. depends on the weight of the floating body
d. none of these

A

c

67
Q

In hindered settling, particles are

a. placed farther from the wall
b. near each other
c. not affected by other particles and the wall
d. none of these

A

b

68
Q

THREE TYPES of centrifugation

A

• Centrifugal Sedimentation
• Centrifugal Filtration
• Centrifugal Decantation

69
Q

The most common type of centrifuge

A

Sharples Centrifuge

70
Q

For the separation of sugar solution from settled out mud, we use

a. sparkler filter
b. plate and frame filter
c. centrifugal filter
d. rotary drum vacuum filter

A

c

Sparkler - has wide usage in pharmaceutical and cosmetic industry

Centrifugal - used whenever the solid particle contaminants in an industrial liquid have a higher density than the liquid itself

P&F - used for fine filtration of liquid products in fruit wine and cider, fruit and vegetable juice, beverages

Rotary drum vacuum - continuous filtration of large quantities of slurries containing a high content of suspended solids.

71
Q

Moisture can be removed from lubricating oil using

a. tubular centrifuge
b. clarifier
c. sparkler filter
d. vacuum leaf filter

A

a

The tubular centrifuge is used primarily for the continuous separation of liquids from liquids or of very fine particles from liquids

72
Q

Which of the following can be most effectively used for clarification of lube oil and printing ink?

a. sparkler filter
b. precoat filter
c. disc-bowl centrifuge
d. sharpless supercentrifuge

A

d

73
Q

Where the difference in density of the two liquid phases to be separated is very small (as in milk cream separator), the most suitable separator is

a. disc bond centrifuge
b. sharpless supercentrifuge
c. batch basket centrifuge
d. sparkler filter

A

a

74
Q

The equation that is applied to describe the flow of a fluid through a porous medium under laminar condition is

a. Fanning-Darcy Equation
b. Ruth Equation
c. Kozeny-Karman Equation
d. Hagen-Poiseuille Equation

A

c

75
Q

The operation by which solids are separated from liquids due to the difference in their respective densities is

a. filtration
b. sedimentation
c. screening
d. adsorption

A

b

76
Q

In a filtration operation involving incompressible cakes, the flow rate is directly proportional to

a. the viscosity of the filtrate
b. the thickness of the filter cake
c. the pressure applied
d. the size of the cake particles

A

c

77
Q

During filtration of a slurry, the filtration rate will start to fall once the pressure drop across the filter medium

a. becomes constant
c. begins to rise
b. begins to fall
d. becomes zero

A

a

78
Q

During filtration on a rotary filter the precipitate is continuously removed from the filter medium by a scrapper in order to

a. prevent the precipitate from mixing with the filtrate
b. maintain a constant pressure drop across the filter
c. keep the filter clean
d. none of these

A

c

79
Q

In filtration, the coarser the filtration medium ________ the constant rate period

a. the shorter
c. the longer
b. does not affect
d. zero

A

c

80
Q

In a plate-and-frame filter press, the rate of filtration is directly proportional to the

a. resistance of the filter cake
c. resistance of the filter medium
b. cross-section of the filter surface
d. viscosity of the filtrate

A

b

81
Q

For a non-washing constant pressure filtration where the resistance of the filter medium is negligible, maximum capacity of the filter is attained when the filtration time is __________ compared to the dumping and cleaning time.

a. less
b. equal
c. greater
d. cannot be determined

A

b

82
Q

In operating a batch filter, which of the following is the correct. method of operation?

a. The slower the flowrate, the more efficient the recovery.
b. Keeping the pressure constant, the rate of flow increases.
c. Keeping the flowrate constant and gradually increase the pressure
d. The particles forming the cake should be large.

A

c

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