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Pharm Y2S2 - Drying
This deck covers key concepts related to drying processes in pharmaceuticals, including definitions, mechanisms, and considerations for drying methods.
Define moisture content.
Amount of water contained in a material
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Key Terms
Term
Definition
Define moisture content.
Amount of water contained in a material
Define moisture by volume.
The number of water molecules per unit by the total number of molecules
Define moisture in air.
The amount of water (kg) per kg of dry air
Define humidity.
Water vapour in air
Define % relative humidity.
Water vapour in air by total moisture that air can hold
What happens to maximum water content when temperature increases?
Also increases
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| Term | Definition |
|---|---|
Define moisture content. | Amount of water contained in a material |
Define moisture by volume. | The number of water molecules per unit by the total number of molecules |
Define moisture in air. | The amount of water (kg) per kg of dry air |
Define humidity. | Water vapour in air |
Define % relative humidity. | Water vapour in air by total moisture that air can hold |
What happens to maximum water content when temperature increases? | Also increases |
Define dew point. | Temperature at which moisture in air both condenses and evaporates at the same rate |
Why may moisture content change during drying? | Evapouration of water Without air exchange, air may become saturated |
Define a hygroscopic material. | Attract and retain water from their surrounding environment |
What is the total moisture of a compound? | Amount of moisture associated with a wet solid |
What is the free moisture of a compound? | Water easily removed from a wet solid (unbound) |
What is the equilibrium moisture of a compound? | Proportion of bound water |
What is solute migration? | Movement of solution in a wet system during drying |
What is intergranular migration? | Movement of solvent between granules towards the surface |
What is intragranular migration? | Separation of granules due to solvent movement |
What factors should be considered when selecting a drying method? | Heat sensitivity Physical characteristics Solvent/liquid for removal Efficient mass transfer of evaporated liquid Efficient vapour removal from air Sterility |
What are the three categories of drying for wet solids? | Convection Conduction Radiation |
What are the features of a fluidised bed dryer? | 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 |
What are the benefits of turbulence in drying? | Particles mix with air maximising surface area of powder bed allowing efficient heat transfer |
What are the disadvantages of turbulence in drying? | May damage granules Small particles may be stuck in fluidising air Movement may induce charges of static |