Drying

Question 1

During manufacturing, drying is essential to guarantee process performances e.g. granulation and compaction. True or false?

Answer 1

True

Question 2

What is moisture content defined as?

Answer 2

The amount of water contained in a material

Question 3

What is % moisture by volume defined as?

Answer 3

The molecules of water per unit volume

Question 4

Moisture content and relative humidity are the same thing. True or false?

Answer 4

False

Question 5

What is humidity defined as?

Answer 5

The amount of water vapour present in the air

Question 6

Relative humidity indicates the amount of moisture in the air as a percentage of the maximum amount of moisture that the air can hold. True or false?

Answer 6

True

Question 7

Water content in the air increases as temperature increases. True or false?

Answer 7

True

Question 8

An increase in temperature results in an increase in relative humidity. True or false?

Answer 8

False - a decrease in relative humidity because the air can hold a greater amount of water vapour

Question 9

What is the dew point?

Answer 9

The temperature to which moisture condenses and evaporates at the same rate

Question 10

During drying, only moisture content can change. True or false?

Answer 10

False - temperature also changes

Question 11

Paper is non-hygroscopic. True or false?

Answer 11

False - it is hygroscopic

Question 12

When there is less moisture in the air, paper releases moisture. True or false?

Answer 12

True

Question 13

When there is more moisture in the air, water absorbs moisture. True or false?

Answer 13

True

Question 14

What is meant by total moisture?

Answer 14

The total amount of water associated with a wet solid

Question 15

Free moisture content is the amount of water that can be easily removed. True or false?

Answer 15

True - also known as unbound water

Question 16

What is meant by equilibrium moisture content?

Answer 16

The portion of water that is more difficult to remove, also known as bound water

Question 17

What are the factors that need to be considered when selecting the drying method?

Answer 17

Heat sensitivity of materials used
Materials physical characteristics
Solvent/liquid to be removed e.g. boiling point
Efficient mass transfer of evaporated liquid
Efficient vapour removal from drying air
Amount of material to be processed e.g. scale up considerations
Sterility

Question 18

What are the advantages of a fluidised bed dryer?

Answer 18

Efficient heat transfer (minimise effects on thermo-sensitive materials)
Homogenous process - movement of particles guarantees drying of all individual ones
Free movement of particles reduces the migration process and separation/aggregation phenomena

Question 19

What are the disadvantages of a fluidised bed dryer?

Answer 19

Turbulence might damage granules
Small particles might need specific attention to be removed from the fluidising air
Particle movement in turbulence and warm environment might cause charges of static electricity

Question 20

Vacuum ovens are generally used for large scale processes. True or false?

Answer 20

False - small scale

Question 21

Which type of dryer is used with heat-sensitive materials?

Answer 21

Freeze-dryer

Question 22

A spray dryer generates a large surface area to promote what?

Answer 22

Heat exchange and heat transfer

Question 23

The higher the flow rate of a spray dryer, the smaller the droplets. True or false?

Answer 23

True

Question 24

In a vacuum oven, a temperature of 25-35 degrees is sufficient to boil water. This is convenient for thermo-sensitive drugs. True or false?

Answer 24

True