Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Clare's lectures semester 2 > Drying > Flashcards

Drying Flashcards

1
Q

What do you need to consider with regards to realtive humidity?

A
  • The amount of moisture in the air

- The amount of water saturated in the air (which is temeprature dependent)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What is relative humidity expressed as?

A

It is expressed as the % of vapour pressure of water vapour in air/vapour pressure of water vapour in air saturated at same group multiplied by 100

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What is the oisture content of a wet solid expressed as?

A
  • Expressed as Kg moisture associated with 1Kg dry solid

- Can be expressed as %

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What is total moisture content?

A

-The amount of liquid associated with a wet solid

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

If the moisture content is said to be 0.5, what does this mean?

A

-It means after complete drying, 0.5 Kg of water will be present per Kg of the moisture-free solid

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What is free moisture content?

A
  • Easily removable water

- Unbound water

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Equilibrium moisture content is more difficult to remove and depends on environment/storage temperature, humidity and nature of solid material. TRUE OR FALSE?

A

TRUE

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What do you need to consider before removing all water? (is it essential?)

A
  • Moisture sensitive material

- Hygroscopic material

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What do you need to consider before removing all water? (is it essential?)

A
  • Moisture sensitive material

- Hygroscopic material

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What are Hygroscopic material?

A
  • They are materials that readily attracts moisture from its surrounding by either absorption or adsorption
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What if he material are exposed to a humid condition?

A
  • Regain moisture? check answer
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What is free moisture lost through?

A

Evaporation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Name the methods of drying?

A
  • Convective drying
  • Conductive drying
  • Radiation drying
  • Spray drying
  • Freeze drying
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Name the two types of Convective drying?

A
  • Static (fixed bed)

- Dynamic (fluidised bed)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Describe static convective drying?

A

-Slow drying process

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What is doen i order to speed up the static convective drying process?

A
  • Turbulent air flow over the surface of drying materials (which is the rate at which vapour is removed)
  • Maintaining the air flow at certain temperature (the rate at which heat transferred)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What is the rate of drying of static convective drying dependent on?

A
  • Constant rate period

- Falling rate period

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

Describe constant rate period?

A
  • Linear relationship

- Drying occurs on the surface

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

It is important to control the rate of heat transfer and the rate of removal of the vapour in constant rate period. TRUE OR FALSE?

A

TRUE

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

The end of the constant rate period=critical moisture content. Is this TRUE for the first falling rate period?

A

yes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

What occurs in first falling rate period?

A
  • The moisture on the solid surafe to be removed not enough to saturate the air in contact with the surface
  • Drying rate devreases
  • Capillary to pendular state
  • Heat should be reduced
  • Beware of solute migration
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

What occurs in the second falling rate period?

A
  • Drying can no longer take place on the surface
  • Drying the solid body of material
  • Rate dependant on removal of water vapour through te pores of the bed
23
Q

What are the advantages of dynamic convective drying?

A
  • Good contact between the wet particles and the air
  • Drying from the surface of each particle, not from the bed
  • Uniform tempearture
  • Efficient drying rates with high output
  • Risk of solute migration prevented
24
Q

What are the advantages of dynamic convective drying?

A
  • Good contact between the wet particles and the air
  • Drying from the surface of each particle, not from the bed
  • Uniform tempearture
  • Efficient drying rates with high output
  • Risk of solute migration prevented
25
Q

What are the disadvantages of dynamic convective drying?

A

-Influence of air velocity can lead to seperation of wet particles

26
Q

Describe conductive drying?

A
  • Materials in thermal contact with a hot surface
  • Drying achieved by conduction
  • Can take place at low temperatures
27
Q

Describe the Vacuum oven in (Conductive drying)

A
  • Static

- Not commonly used for drying in production

28
Q

Describe the Vacuum oven in (Conductive drying)

A
  • Static

- Not commonly used for drying in production

29
Q

Describe the vacuum tumbling drier in (Conductive drying)

A
  • Higher heat transfer than vacuum oven

- More popular than vacuum oven

30
Q

Describe Radiation drying?

A
  • No heat transfer medium

- Heat energy transferred via radiation

31
Q

Name the two types of radiation drying?

A
  • Infrared radiation

- Microwave radiation

32
Q

Describe infrared radiation?

A
  • Absorbed rapidly
  • Shallow penetration
  • Not common in pharmaceutics
33
Q

Describe Microwave radiation?

A
  • Better penetration
  • Rapidly drying at lower temperatures
  • Uniform heat transfer
  • Solute migration minimised
  • Static bed
34
Q

Spray drying provides large area for heat and mass transfer. TRUE OR FALSE?

A

TRUE

35
Q

Spray drying atomises liquid into stream of hot air. TRUE OR FALSE?

A

TRUE

36
Q

Describe spray drying?

A
  • Droplets sprayed into stream of hot air
  • Droplets dry into individual solid particle
  • Particle formation and drying occur in one step
37
Q

In spray drying particle sixe is controlled by droplet size which is controlled by atomizer. TRUE OR FALSE?

A

TRUE

38
Q

Atomiser experiences build up of solid. TRUE OR FALSE?

A

FALSE

39
Q

In spray drying, AIr rotates in chamber tangentially increasing droplet residence time (drying time). TRUE OR FALSE?

A

TRUE

40
Q

What is spray drying used for?

A

Almost any substance in solution or suspension e.g citric acid, strach

41
Q

What are the advantages of spray drying?

A
  • Millions of small droplets give large surface area so evaporation is rapid
  • Rapid evaporation means droplets do not attain high temperatures
  • Uniform sized spherical particles
  • Characteristic particle form allows efficient packaging
  • Increased dissolution rate and bioavialbility of poorly water soluble drugs
  • Low labour costs
  • Can be used as a continous process
42
Q

What are the disdavantages of spray drying?

A
  • Equipment bulky and expensive

- Thermal efficiency quite low

43
Q

What is Freeze drying used for?

A

-Heat sensitive materials or materials which are excessively hygroscopic

44
Q

Describe Freeze drying?

A
  • Drying without excessive damage

- Solvent undergoes solid-gas sublimation

45
Q

What are the 4 processes of sublimation?

A
  1. Liquid freezes
  2. Pressure reduction
  3. Increasing heat
  4. Sublimation occurs
46
Q

What are the advantages of freeze drying?

A
  • Low temperature drying reduces product degradation
  • Product is light and porous
  • Porous product is readily soluble
  • No concentration of solution prior drying
  • Oxidation minimized
47
Q

What are the disdavantages of freeze drying?

A
  • Product extremely hygroscopic - need careful packaging

- Slow compliacted process

48
Q

What is solute migration?

A

The movement of soluble drugs or excipients to the surface of the particles during drying

49
Q

How does solute migration occur?

A
  • As solvent being evaporated moves to the surface the dissolved solutes move with them
  • Results in localised concentrations of drugs/excipients at surface
50
Q

What are the disadvantages of solute migration?

A
  • Tablets/ Granules aren’t uniform

- Quality control problems

51
Q

What are the two mechanisms of granule drying?

A
  • Intergranular migration

- Intragranular migration

52
Q

Describe intergranular migration

A
  • Between granules
  • Solutes (drug/excipients) migrate granule to granule
  • Common in static convective drying
53
Q

Describe intragranular migration

A
  • within individual granules
  • Solute moves towards pheriphery of granule leading to uneven distribution
  • Common in dynamic convective drying and vacuum tumbling drying
54
Q

How can migration be prevented?

A
  • Water insoluble dyes
  • Increased viscosity of granulating fluid
  • Mninimize/optimise volume of granulating fluid
  • Remixing of granules prior to tableting

Clare's lectures semester 2 (10 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions