Solids Isolation

Question 1

Define polymorphism

Answer 1

Ability to crystallise in more than one form

Question 2

Define enantiotropic

Answer 2

Interconvertible polymorphs

Question 3

Define monotropic

Answer 3

polymorphs are incapable of transformation

Question 4

Crystal Types

Answer 4

• Amorphous
• Polymorphs
• Hydrates
• Solvates
• Salts
• Co-Crystals

Question 5

Eutectic Point

Answer 5

Mass fraction at which two solids will dissolve together

Question 6

Congruent melting point

Answer 6

Hydrate can exist in equilibrium wuat a solution of the same composition

Question 7

Define the critical radius

Answer 7

• Smallest crystal radius that can exist in a solution of a given concentration

(very small pasticles are unstable and will break up)

Question 8

Size dependent solubility equation

Answer 8

c(r) = c_inf x exp{(2gamma x V_m)/(rRT)}

c_inf = solubility of macroscopic particle
Gamma = solid-liquid interfacial tension
V_m = Molar volume

Question 9

Theoretical Nucleation Rate Equation

Answer 9

B = K_B x exp{(-16gamma^3 V_m^2) /(3R^3 T^3 sigma^2)}

Question 10

Empirical Nucleation Rate Equation

Answer 10

B = K_B x Delta(C)^b

Question 11

3 Crystal Growth Regimes

Answer 11

• Continuous (many growth sites)
• Surface Nucleation (Several nuclei)
• Spiral growth (single nucleus)

Question 12

Crystal Habit

Answer 12

• Growth Rates are generally not identical along crystal facets
• Specific adsorption of particular facets can modify crystal growth

Question 13

Internal vs External Cooling Crystalliser

Answer 13

Internal
- Heat transfer coefficient is connected with the flow regime (Re)

External

• Decouples the hydrodynamic regime from the heat transfer coefficient ar the heat transfer surface
• Can increase Re, heat transfer coefficient and nucleation rate by changingn agitation rate
• Risks deposition of material in the heat exchanger

Question 14

Mixed-Suspension mixed-product removal (MSMPR) Crystalliser

Answer 14

• Ideally mixed
• Steady-state, continuous operation
• No crystals in feed
• no agglomeration or breakage
• size independent growth rate