crystallization
TRANSCRIPT
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CRYSTALLIZATION
Presented By: RABIA IJAZRegistration no. 2013-MS-CH-13
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Crystallization basics Crystal geometry Crystal properties Solid-Liquid Phase Equilibrium Crystallization techniques Mechanism of crystallization
◦ Nucleation◦ Crystal growth
Crystal Size Distribution (CSD) Factors effecting crystallization Batch crystallization Melt crystallization Design consideration Conclusions
TOPICS TO STUDY
Crystallization 3
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What is crystallization?◦ Formation of solid particles within homogeneous
phase What is the objective of crystallization?
◦ High purity◦ Good yield
What are the principles of crystallization?◦ Purity◦ Yield◦ Equilibria
Understanding Crystallization
Crystallization 4
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There are seven basic crystal shapes, also called lattices. They are ◦ Cubic,◦ Trigonal◦ Triclinic◦ Orthorhombic◦ Hexagonal◦ Tetragonal◦ Monoclinic
Crystal Geometry
Crystallization 5
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Crystallization 6
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Anisotropic Liquid Crystal Amorphous Polymorphous
Crystal Properties
Crystallization 8
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Slow Crystallization
What Happens during Crystallization?
Crystallization 9
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Quick Crystallization
Continued…
Crystallization 10
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Solid-Liquid phase Equilibrium
Crystallization
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12Crystallization
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Crystallization by cooling◦ It is chosen when the solubility of solute varies
with the temperature Crystallization by Evaporation
◦ It is chosen when solubility of solute is nearly independent of temperature
Crystallization Techniques
Crystallization
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Nucleation Crystal growth
Nucleation◦ formation of new crystals◦ Primary nucleation◦ Secondary nucleation
Mechanism of Crystallization
Crystallization
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Rate of nucleation:
R= Gas constant C= frequency factor molar volume of crystal v= no. of ions per molecule of solute
Continued…
Crystallization
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16Crystallization
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Deposition of solid material on existing crystals◦ Solid growth◦ Liquid growth◦ Vapor growth
Growth Rate:
∆L Law◦ ∆L= G ∆t
Crystal growth
Crystallization
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Important parameter of crystalline product Correct crystal size vital for economic
production Crystals produced in commercial
crystallization processes are usually small◦30 to 100 um in diameter
Population Density Function
Crystal Size Distribution (CSD)
Crystallization
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Super saturation Time Temperature Impurities in solution Rate of stirring
Factors effecting crystallization
Crystallization
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Low capacity Seed crystals added Maintain suitable level of super saturation
Batch Crystallization
Crystallization
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Separation without solvent Purify products of low thermal stability Carried out in:
◦ Suspension◦ By passing melt through cooled tubes
Melt crystallization
Crystallization
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Important parameters involved in design of crystallizer◦ Feed rate & state◦ Desired crystal size distribution (CSD) & yield◦ Solvent evaporation rate & heat transfer area
required◦ Crystallizer volume◦ Crystallizer dimension
Design Considerations
Crystallization
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CONCLUSIONS
Crystallization
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The main point in crystallization is to achieve super saturation.
Crystal Size Distribution is main parameter. Crystal formation is start by two steps:
◦ Nucleation◦ Crystal growth
Conclusions
Crystallization
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Warren L. McCabe, Julian C. Smith, Peter Harriott. Chapter # 27, Unit Operations of Chemical Engineering
Principles of mass transfer & separation processes. Binary K. Dutta, PHIlearning private limited.
Understanding crystallization & crystallizer by Ketan D. Samant, Lionly O’Young, clear waterbay technology, Inc.
http://orgchem.colorado.edu/Technique/Procedures/Crystallization/Crystallization.html
Reference
Crystallization
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