SIZE ENLARGEMENT

Question 1

What is size enlargement?

Answer 1

The process by which smaller particles are put together to form larger masses in which the original particles can still be identified.

Size enlargement is a critical step involving particulate solids in various process industries.

Question 2

What are the industries in which size enlargement is used?

Answer 2

• Pharmaceutical
• Food
• Agricultural

These industries utilize size enlargement for various applications.

Question 3

What are the objectives of size enlargement?

Answer 3

• Reduction of dust hazard
  *Reduction of caking and lump formation
• Improve flow properties
• Increase bulk density for storage
• Create non-segregating mixtures of ingredients of differing original size
  *Provide a defined metered quantity of active ingredient
• Control of surface to volume ratio

These objectives help in optimizing material handling and processing.

Question 4

What are Van der Waals forces?

Answer 4

Weak intermolecular forces that are dependent on the distance between atoms or molecules, arising from the interactions between uncharged atoms/molecules.

These forces play a significant role in particle interactions.

Question 5

What are electrostatic forces?

Answer 5

A result of interparticle friction or through the generation of opposite charges.

Electrostatic forces can affect particle behavior during size enlargement.

Question 6

What are liquid and solid bridges in the context of size enlargement?

Answer 6

Dispersion of liquid into a powder mass generally results in a significant increase in the strength of particle-particle agglomerates.

These bridges enhance the cohesion between particles.

Question 7

What are the size enlargement rate processes?

Answer 7

• Compaction
• Granulation
• Encapsulation
• Pelletizing
• Agglomeration

Each of these processes plays a unique role in size enlargement.

Question 8

What is granulation?

Answer 8

The process of forming grains or granules from a powdery or solid substance, producing a granular material.

Granulation is widely used in the chemical and pharmaceutical industries.

Question 9

What are the reasons for granulation?

Answer 9

• To prevent segregation of powder mix
• To improve flow characteristics
• For improving compression ability

Granulation enhances the handling and processing of powders.

Question 10

What is wet granulation?

Answer 10

A method of granulation that involves the addition of a liquid to a powder to form granules.

This technique is essential in producing uniform granules.

Question 11

What is the first step in the mechanism of wet granulation?

Answer 11

Nucleation, where granulation starts with particle to particle contact and adhesion due to liquid bridges.

Nucleation is crucial for the formation of granules.

Question 12

What are the three states describing the distribution of liquid between particles in wet granulation?

Answer 12

• Pendular State
• Funicular State
• Capillary State

These states illustrate the varying degrees of liquid presence between particles.

Question 13

What is the process of wetting in granulation?

Answer 13

The process by which air within the voids between particles is replaced by liquid, governed by surface tension and contact angle.

Wetting influences the efficiency of granulation.

Question 14

What is granule breakage?

Answer 14

The fracture of a granule to form two or more pieces.

Breakage can impact the quality of the final granules.

Question 15

What is attrition in the context of granulation?

Answer 15

The reduction in size of a granule by loss of primary particles from its surface.

Attrition can lead to undesirable changes in granule characteristics.

Question 16

Fill in the blank: The size enlargement process that transforms a powder material into large entities is called _______.

Answer 16

Granulation

Question 17

True or False: The capillary state is when all air has been displaced from between the particles.

Answer 17

True

Question 18

Fill in the blank: _______ is the process of compressing or molding a material into the shape of a pellet.

Answer 18

Pelletizing

Question 19

At what level of spray flux will show drop footprints will not overlap and each drop will form separate nucleus granule

Answer 19

low

Question 20

What is the PENDULAR STATE?

Answer 20

Usually at low moisture level, particles are held together by lens-shaped rings of liquid, with mainly air between the particles.

This state indicates low moisture content in the material.

Question 21

What characterizes the FUNICULAR STATE?

Answer 21

It is an intermediary state where air starts to displace from between particles.

This state indicates a transition from low moisture to higher moisture levels.

Question 22

What occurs in the CAPILLARY STATE?

Answer 22

All air has been displaced from between the particles; liquid penetrates the pores and forms a solid bridge between particles, resulting in the strongest adhesion when the liquid evaporates.

This state signifies maximum moisture content and strong particle adhesion.

Question 23

there will be significant overlap of drops hitting the
powder bed

Answer 23

At high spray flux

Question 24

when spray flux is high, spray flux is

Answer 24

𝝍𝒂 ≈ 𝟏

Question 25

At low spray flux

Answer 25

𝝍𝒂 ≪ 𝟏

Question 26

The parameter that determines whether coalescence will occur is

Answer 26

Stokes number

Question 27

a measure of the ratio of collisional kinetic energy to energy dissipated through viscous dissipation

Answer 27

Stokes number

Question 28

For coalescence to occur, Stokes number must be

Answer 28

less than the critical value Stk*

Question 29

What type of motion is imparted to particles in tumbling granulators?

Answer 29

A tumbling motion ## Footnote This motion occurs in an inclined cylinder or a pan.

Question 30

What is a key operational characteristic of tumbling granulators?

Answer 30

Operate in continuous mode and can handle large throughputs ## Footnote This allows for efficient processing of materials.

Question 31

What does the tumbling action in granulators lead to?

Answer 31

Natural classification of contents according to size ## Footnote This helps in sorting particles during the granulation process.

Question 32

How is the motion of particles achieved in mixer granulators?

Answer 32

By an agitator rotating at low or high speed ## Footnote The axis of rotation can be vertical or horizontal.

Question 33

What is the range of rotation speeds for horizontal pug mixers used for fertilizer granulation?

Answer 33

50 rpm to over 3000 rpm ## Footnote This varies depending on the application and equipment used.

Question 34

What is the impeller speed range for vertical axis mixers in the pharmaceutical industry for mixers less than 30 cm in diameter?

Answer 34

500 to 1500 rpm ## Footnote Larger mixers, over 1 m in diameter, have lower speeds of 50–200 rpm.

Question 35

What sets particles in motion in fluidized bed granulators?

Answer 35

Fluidizing air ## Footnote This can create either a bubbling or spouted bed.

Question 36

What operational modes can fluidized bed granulators operate in?

Answer 36

Batch or continuous mode ## Footnote This flexibility allows for various production processes.

Question 37

What are some advantages of fluidized bed granulators?

Answer 37

Good heat and mass transfer, mechanical simplicity, ability to produce small granules from powder feeds ## Footnote These advantages make them suitable for various applications.

Question 38

What must happen for two colliding primary granules to coalesce?

Answer 38

Their kinetic energy must be dissipated ## Footnote This is crucial for forming a strong bond.

Question 39

What must the strength of the resulting bond be able to resist?

Answer 39

External forces exerted by the agitation of the powder mass ## Footnote This is important to maintain granule integrity during processing.