Size Enlargement

Question 1

It is a particle that are set in motion by air and may be operate in batch and continuous mode.

Answer 1

Fluidized bed granulators

Question 2

Fracture of a granule to form two or more pieces.

Answer 2

Fragmentation

Question 3

Operates in continuous mode and able to deal with large through-puts.

Answer 3

Tumbling granulators

Question 4

It occurs when there is a long period during which no increase in size occurs.

Answer 4

Induction Growth

Question 5

It results in larger particles than those formed in spray dryers.

Answer 5

Prilling

Question 6

The size distribution of particles in an agglomeration process; it is determined by the kinetics of the many processes occurring simultaneously.

Answer 6

Population balance

Question 7

Increase in particle size but not in total mass of particles

Answer 7

Coalescence

Question 8

Generating nuclei that re-enter the cycle again

Answer 8

Attrition

Question 9

Particles are ‘tumbled’ in an open cylinder, roughened walls were subjected to a combination of gravitational and centrifugal forces.

Answer 9

Drum Agglomerators

Question 10

Particularly used with large particles, the rapid circulation within the bed gives rise to a high level of inter-particle impacts.

Answer 10

Spouted beds

Question 11

For solid particles, the propensity ________ with particle size because of the availability of a larger number of weaker microcracks. Hence, larger particles break more ________ than smaller particles.

Answer 11

increases ; frequently

Question 12

Briquetting machines are used to create briquettes of material by compacting smaller pieces together. The following are the advantages of using briquetting machines except?

Answer 12

Rollers can wear down quickly

Question 13

Like breakage frequency, the average number of daughter particles is dependent on _____________.

Answer 13

Particle Size

Question 14

I. Pellet mills compact powder in a confined space via a process called pressure agglomeration.
II. The pressure is increased in the compression step, causing brittle particles to break and malleable particles to deform.

Answer 14

Both statements are True

Question 15

This is the size distribution of daughter particles resulting from breakage of particles of a particular size.

Answer 15

Daughter distribution function

Question 16

Disc granulators, or pelletizing discs as they are known in the ore industry, work based on the tumbling technique of agglomeration. ______, magnetic, and electrostatic forces bind the agglomerates together. The strongest force against agglomeration is the ______ of the solid.

Answer 16

Van der Waals ; weight

Question 17

Aggregation efficiency is a function of size of both the aggregating particles in the pair and is denoted by______.

Answer 17

a(x, x′ )

Question 18

The powder is chopped and mixed to produce a fine, free-flowing powder. Then a liquid binder is blended with the powder to produce granules.

Answer 18

Mixer Granulator

Question 19

The ________ is usually a function of particle size and is denoted by Γ(x). The Γ(x) provides the fraction of particles that will break per unit ____

Answer 19

breakage frequency ; time

Question 20

In __________, molten input is picked up by a rotating drum and moves toward the outer surface of the drum.

Answer 20

Thermal Agglomeration

Question 21

It is a process by which smaller particles are put together to form larger masses in which the original particles can still be identified

Answer 21

Size Enlargement

Question 22

Size enlargement is one of the single most important process steps involving ___________in the process industries.

Answer 22

Particulate Solids

Question 23

Size enlargement is mainly associated with the

Answer 23

All of the above

Question 24

Methods by which size enlargement is brought about include granulation, compaction (e.g. tabletting), extrusion, _______, spray drying and prilling.

Answer 24

Sintering

Question 25

I: Agglomeration is the formation of agglomerates or aggregates by sticking together of larger particles and granulation is agglomeration by agitation methods II: There are many reasons why we may wish to increase the mean size of a product or intermediate

Answer 25

Only statement II is true

Question 26

These are specifically important to granulation processes

Answer 26

Liquid Bridge Forces

Question 27

The rate processes are important to granulation and _____________ included in order to develop a ________ model for simulation for the granulation process.

Answer 27

Population Balance ; simple

Question 28

There exist between all solids molecularly based attractive forces collectively known as

Answer 28

van der Waals forces

Question 29

The energy of these forces is of the order of ____ eV and decreases with the _____ power of the distance between molecules.

Answer 29

0.1 ; 6th

Question 30

The attractive force, Fvw, between a sphere and a plane surface as a result of van der Waals forces was derived by ____________

Answer 30

Hamaker (1937)

Question 31

Granules formed by _________ are usually not the ______ product in a granulation process.

Answer 31

Liquid Bridges ; end

Question 32

Solid bridges between particles may take three forms:

Answer 32

Crystalline Bridges, Liquid Binder Bridges, and Solid Binder Bridges

Question 33

If the material of the particles is soluble in the liquid added to create granules, crystalline bridges may be formed ________________.

Answer 33

When the liquid evaporates

Question 34

I: The process of evaporation reduces the proportion of liquid in the granules producing high strength pendular bridges after crystals form. II: The liquid used initially to form the granules may contain a binder or glue which takes effect upon evaporation of solute.

Answer 34

Both Statements are false

Question 35

This is a finely ground ______ which reacts with the ______ present to produce a solid _______ to hold the particles together.

Answer 35

Solid ; Liquid ; Cement

Question 36

The relative importance of the forces varies with changes in _______ properties and with changes in the humidity of the surrounding _______.

Answer 36

Particle ; Atmosphere

Question 37

There is considerable interaction between the _____________

Answer 37

Bonding Forces

Question 38

In aqueous systems adsorbed moisture can considerably increase ___________.

Answer 38

Van der Waals Forces

Question 39

I: Absorbed moisture can also reduce interparticle friction and potential for interlocking, making the powder more free-flowing. II: Liquid Bridges Forces decay rapidly if the humidity of the surrounding air is increased.

Answer 39

Both statements are false

Question 40

If humidity is further increased liquid bridge formation can result in a return to cohesive behaviour. This effect has been reported in powder mixing studies by _________

Answer 40

Coelho and Harnby (1978) and Karra and Fuerstenau (1977)

Question 41

When the granules are very weak (Stdef > 0.2), they fall apart due to collisions and no granule growth occurs. This is the _______.

Answer 41

Crumb Regime

Question 42

All collisions between wet granules will lead to coalescence and the rate of growth will be high. Stv < Stv*.

Answer 42

Non-inertial Regime

Question 43

No collisions lead to coalescence. Granules grow very slowly by layering only. Stv > Stv*

Answer 43

Coating Regime

Question 44

Some collisions will lead to coalescence. The rate of granule growth will be moderate and sensitive to formulation or process parameters that change Stv. Stv ≈ Stv*.

Answer 44

Inertial Regime

Question 45

When two granules collide within the granulator, what will the collision lead to if Stv > Stv*.

Answer 45

Rebound

Question 46

If the viscous Stoke number of two colliding granules is Stv < Stv* , what will happen?

Answer 46

Coalescence

Question 47

In this growth behavior, granules quickly reach a minimum porosity and there is lots of deformation on collision.

Answer 47

Steady Growth

Question 48

Where granules grow in size very quickly and any induction time is reduced to zero, this growth behavior occurs at very high liquid saturations.

Answer 48

Rapid Growth

Question 49

A simulation process used by engineers that is the suitable approach for wet agglomeration processes when more mathematics or precision are required

Answer 49

Population Balance Modeling

Question 50

A simulation process that is suitable for the compaction process because it uses a numerical method useful for computing stresses in solids under load and deformation.

Answer 50

Finite Element Analysis

Question 51

The primary potential driving forces for sintering includes; (except)

Answer 51

A dense Solid

Question 52

Low vacancy concentration; Concave Surface, High vacancy concentration; Convex Surface

Answer 52

Both Statements are false

Question 53

In polycrystalline materials, the mass transport ways that are responsible for sintering are; (except)

Answer 53

plastic diffusion

Question 54

Layering is the dominant growth mechanism in the coating regime and is therefore most important for beds of large granules and low binder viscosity e.g. ammonium nitrate granulation, urea prill fattening and coating applications. Consolidation has a strong effect on the final porosity of granules produced by coalescence.

Answer 54

Both statements are true

Question 55

Low density, high velocity spout through which most of the air travels; and a low density, moving bed annular region through which air percolates at a low velocity.

Answer 55

Only statement I is true

Question 56

Mixer granulators find wide application for;

Answer 56

Construction

Question 57

Four major classes of particulate caking: (Except)

Answer 57

Physical Caking

Question 58

Green agglomerates are formed from solid particles and binder. Green agglomerates are not cured

Answer 58

Only statement I is true

Question 59

The mode of operation to achieve and control agglomeration is characterized by several consecutive steps; (except)

Answer 59

Cutting

Question 60

Spray drying represents an attractive alternative to traditional granulation and feed preparation methods used. Atomization of the liquid feed and contacting the spray with air are the critical features of spray dryers

Answer 60

Both statements are true