8/13/2019 Crystall is Er
1/12
Lesson 7.1 INTRODUCTION TO
CRYSTALLIZATION
In this chapter, our discussion on crystallization is
restricted to the crystallization from liquid solution.
Crystallization is a unit operation that involves
the separation of a solute from its solution in the form of
crystals.
Crystallization involves simultaneous heat and
mass transfer.In crystallization, mass transfer takes place from
solution to solid crystalline phase.
Here phases in contact are (1) liquid and (2) solid.
8/13/2019 Crystall is Er
2/12
8/13/2019 Crystall is Er
3/12
Lesson 7.2.1 METHOD OF SUPER
SATURATION
Supersaturation:
Supersaturation is the quantity of the solutepresent in
the solution in which crystals are growing compared with
the quantity of the solute that is in equilibrium withthe solution. The supersaturation may be expressed as a
coefficient s which is given as
Agitated tank crystallizer:
Scrapped surface crystallizer:
(1) Swenson-walker crystallizer and
(2) Double pipe crystallizer.
8/13/2019 Crystall is Er
4/12
Lesson 7.2.1 METHOD OF SUPER
SATURATION
Swenson-walker crystallizer:
The Swenson-walker crystallizer is a cooling type,
continuous, jacketed trough crystallizer.
It is an example of the scrapped surface crystallizer
andis probably most widely used crystallizer.
8/13/2019 Crystall is Er
5/12
Lesson 7.3 INTRODUCTION TO DRYING
Drying is frequently the last operation in the
manufacturing process and is usually carried after
evaporation, filtration, or crystallisation.Moisture content on wet basis : It is expressed as the
ratio of weight of moisture to the weight of wet feed
material. If X is the kg moisture associated with one
kg of dry solids then.
Moisture content on wet basis = X
1+X
8/13/2019 Crystall is Er
6/12
Lesson 7.3 INTRODUCTION TO DRYING
Equilibrium moisture content (X*) : The moisture
content of substance that is in thermodynamic equilibrium
with its vapour in gas phase under specified humidity andtemperature of gas is termed equilibrium moisture content.
Constant rate period : It is that part of the drying
process during which the rate of drying expressed as
the moisture evaporated per unit time, per unit area of
drying surface, remains constant.Falling rate period :It is that part of the drying process
during which the rate of drying varies with time and
instantaneous drying rate expressed as amount ofmoisture evaporated per unit time.
8/13/2019 Crystall is Er
7/12
0=F \U Z[8G[ V;Z SZTF\ 5ZLA/F[HIFZ[ U[; VYJF CJFGF[ J[U J3] CF[I K[ tIFZ[ 0=F.\UGF[ Z[8 56 J3]CF[I K[P
H[D ;F5[ CI]lDl0l8 VF[KL CF[I K[ T[D K[P0=F.\UGF[ Z[8 56 J3] CF[I
U[; VYJF CJFGF ;\5S"DF\ VFJTL ELGL ;5F8LG]\ [+O/ J3] CF[I
TF[40=F.\UGF[ Z[8 J3] CF[I K[PHIFZ[ U[;GF TF5DFGDF\ J3FZF[ YFI K[ tIFZ[ ;F5[ CI]lDl0l8DF\ 38F0F[YFI K[ VG[ T[YL 0=F.lJ\U OF[;"DF\ J3FZF[ YFI K[ T[YL 0=F.\U Z[8DF\
J3FZF[ YFI K[P
Lesson 7.3.1 FACTOR EFFECTING ON
DRYING RATE
8/13/2019 Crystall is Er
8/12
Lesson 7.4 CLASSIFICATION OF DRYER
1. Tray dryer.
2. Rotary dryer.3. Direct-indirect type dryer.
4. Drum dryer.
5. Spray dryer.6. Fluidised bed dryer.
7. Tunnel dryer.
8. Flash (pneumatic) dryer
8/13/2019 Crystall is Er
9/12
Lesson 7.4 SINGLE DRUM & DOUBLE DRUM
DRYER
8/13/2019 Crystall is Er
10/12
Lesson 7.4.1 THIN FILM DRYER DRYER
8/13/2019 Crystall is Er
11/12
Drying is removal of small
amount of moisture from theSubstance below its boiling
point.
Generally hot gas or steam is
used for this operation.
Types of dryer are:Rotary drum dryer , spray Dryer
Vacuum dryer , peddle dryer,
Tray dryer , fluid bed dryer.
Lesson 7.4.2 VACUUM DRYER
8/13/2019 Crystall is Er
12/12
Lesson 7.5 PRECAUTIONS FOR DRYING
*TO BE EXAMINED THE PRILLS FROM SPRAY DRYER
*TO BE CHECK VACUUM
*TO BE CHECK TEMPERATURE
* TO BE CHECK PRESSURE
* TO BE CHECK NOISE
* TO BE CHECK CYCLONE BUILDUP
Top Related