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Pharm Y2S2 > Drying > Flashcards

Drying Flashcards

1
Q

Define moisture content.

A

Amount of water contained in a material

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2
Q

Define moisture by volume.

A

The number of water molecules per unit by the total number of molecules

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3
Q

Define moisture in air.

A

The amount of water (kg) per kg of dry air

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4
Q

Define humidity.

A

Water vapour in air

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5
Q

Define % relative humidity.

A

Water vapour in air by total moisture that air can hold

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6
Q

What happens to maximum water content when temperature increases?

A

Also increases

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7
Q

Define dew point.

A

Temperature at which moisture in air both condenses and evaporates at the same rate

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8
Q

Why may moisture content change during drying?

A

Evapouration of water

Without air exchange, air may become saturated

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9
Q

Define a hygroscopic material.

A

Attract and retain water from their surrounding environment

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10
Q

What is the total moisture of a compound?

A

Amount of moisture associated with a wet solid

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11
Q

What is the free moisture of a compound?

A

Water easily removed from a wet solid (unbound)

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12
Q

What is the equilibrium moisture of a compound?

A

Proportion of bound water

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13
Q

What is solute migration?

A

Movement of solution in a wet system during drying

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14
Q

What is intergranular migration?

A

Movement of solvent between granules towards the surface

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15
Q

What is intragranular migration?

A

Separation of granules due to solvent movement

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16
Q

What factors should be considered when selecting a drying method?

A 
Heat sensitivity
Physical characteristics
Solvent/liquid for removal
Efficient mass transfer of evaporated liquid
Efficient vapour removal from air
Sterility
17
Q

What are the three categories of drying for wet solids?

A

Convection
Conduction
Radiation

18
Q

What are the features of a fluidised bed dryer?

A

Optimised contact between warm drying air and wet powder
Increased air velocity causes pressure drop with powder suspended in air
Powder free to move with further increase in velocity
Capacity 0.4-1.2kg
Drying time 20-40 minutes

19
Q

What are the benefits of turbulence in drying?

A

Particles mix with air maximising surface area of powder bed allowing efficient heat transfer

20
Q

What are the disadvantages of turbulence in drying?

A

May damage granules
Small particles may be stuck in fluidising air
Movement may induce charges of static

Pharm Y2S2 (26 decks)

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