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Types of Crystallization used in chemical industry
Crystallization a separation process used in chemical industry- Crystallization is most widely used unit operation in Chemical industry. This operation is use for separation purpose. In this process we can do solid liquid separation .So in this article we will study about crystallization separation process used in chemical industry, factors affecting crystallization , seeding , types of stirrer use for crystallization.
What is crystallization ?
In short Crystallization is nothing but formation of crystals .
Is crystallization is unit operation or unit process ?
Yes crystallization is unit process .
Types of Crystallization used in chemical industry
On the basis of Crystallization method , crystallization can be classified as ,
- Crystallization by cooling/chilling
- Crystallization by evaporation
Crystallization by cooling or chilling
In this type of crystallization technic , first we cool or chill the solution up to a particular temperature as per solubility of solute in solvent. In short in this process we can cool or chill the solution up to the temperature where almost all solute get solidify .After this we need to separate this solid and liquid using suitable filtration method like centrifuge. Almost all pharmaceutical industry as well as chemical industry use centrifuge to separate the solid crystal from the liquid. In case if solvent have HAZRDUS property then we can choose some other method of filtration.This is widely used method in chemical industries.
In short in crystallization by cooling or chilling we chill the solution up to a particular temperature then we can do filtration using centrifuge . After centrifuge we will get solid as our solute and liquid as mother liquor.
Process flow diagram for types of crystallization used in chemical industry
Crystallization by evaporation
In crystallization by cooling we do solidification by reducing the temperature. In crystallization by evaporation we evaporate the excess solvent by heating the solution. After evaporation of excess solvent we can do filtration to separate the solid from liquid.
In above method we can evaporate the excess solvent depending on solubility of solute in the solvent.(crystallization process flow diagram)
Factors affecting crystallization
Factors affecting crystallization is very important for chemical engineers.
Performance of crystallization is depends on some factors like.
- Temperature
- Solubility
- Types of agitator and its RPM
- Degree of inversion
- Crystallizing substance property
- Nuclei Formation
- Seeding
- Crystallization rate
Temperature of crystallization
As we know that solubility of of material is different at different temperature , so we need find the suitable temperature for crystallization as per solubility data .
Solubility of material
Solubility is very important for crystallization of material. As we know that crystallization is unit process used for separation or purification of product. So we need to salect a solvent as per solubility of our material at perticular temperature.
Types of agitator and speed of agitator
A agitator and its RPM play a very important role in crystallization . In Chemical industry mostly anchor type stirrer is used for crystallization. High crystallization rate is responsible for small crystal size. Very high agitation rate become resistance for formation of crystals. Mixing is get affected by motion of liquid .
Why anchor types of stirrer is mostly used for crystallization in Chemical and pharmaceutical industry ?
Anchor types of stirrer used in Chemical industry is due to some very important application. The main advantage of anchor types of stirrer use is ” it’s give very high heat transfer rate “. Anchor type of stirrer is very close to the vessel so it give a very good heat transfer rate . Also speed of anchor types of stirrer is slow as compared to other types of stirrer .
Seeding for growth of crystals
Seeding is very important in the crystallization process.
What is seeding process used in crystallization ?
Seeding process is nothing but addition of material or mass in crystallizating solutions which initiate the formation of crystals.
Effect of nucleation in Crystallization
This is first step of crystallization which gives start to formation of crystal . Nucleation can be classified as homogeneous nucleation and heterogeneous nucleation.
What is nucleation I short ?
Nucleation is formation of small crystals .
After formation of crystals next step is growth of crystals . In crystal growth process ,small small crystal are get attached and form a big crystal.
Conclusion
Article cover basic knowledge about Types of Crystallization used in chemical industry. It cover factors affecting crystallization too. It gives information about Seeding in the formation of crystals .
Read Also ,
azeotropic distillation an overview
different types of condenser used in chemical industries
