Drying Flashcards
(47 cards)
What is drying?
Mass transfer of volatile component out of a solid-liquid mixture
What is drying important for?
Purification of drug + granulation for tabletting
What does moisture content effect?
Product stability
Physical properties
What can H2O do?
Cause microbial growth
Affect degradation = increase hydrolysis
Clump together = decrease flowability
What is a substance called that is normally a gas?
Gas
What is a substance called that is normally a liquid?
Vapour
What is it called when goes liquid to gas?
Vaporisation
Evaporation
Liquid surface only
= below boiling point
Boiling
Throughout body of liquid
= at boiling point only
Solid to gas
Sublimation
Gas to liquid
Condensation
Liquid to solid
Freezing
Gas to solid
Deposition
Solid to liquid
Melting
Liquid to gas
Vaporisation
What will it have if it has a large SA?
Effective heat transfer
Effective mass transfer
What is the equation for heat transfer?
Q = hAΔT
Q = heat transfer
h = heat transfer coefficient
A = SA
ΔT = Temp difference (k)
What is relative humidity (RH)?
H2O content in air
Affects eqm moisture content in solids
What RH equation?
RH (%) = Pcurrent
————-
Psaturation
p = partial pressure
What does it mean higher relative humidity?
Closer to saturation point
= harder liquid is to evaporate
= lower drying rate
What does it mean H2O evaporating off?
Increases surrounding humidity
= if vapour NOT cleared quickly
= drying decreases
What does it mean if sample is in high humidity environment?
Sample gains moisture
What is FMC?
Free moisture content
= unbound H2O
= readily removed by evaporation
What is EMC?
Eqm moisture content (EMC)
= bound H2O
= NOT removed by evaporation
