Evaporation, evaporation equipments, and factors effecting the evaporation rate

2. EVAPORATION:
18ch17

3. CONTENTS;
• Evaporation process
• Objectives of evaporation
• Evaporation equipment (Evaporator)
• Parts of evaporator
• Problems occurring in evaporator
• Types of evaporator
• Potential hazards
• Environmental applications of evaporator

6. OBJECTIVE OF EVAPORATION:
• The objective of evaporation is to concentrate a solution
consisting of a non volatile Solute and a volatile solvent.
1. Evaporation is conducted by vaporising a portion of
the solvent to produce concentrated solution of thick
liquor.
2. In evaporation the thick liquor is the valuable
product and the vapours are condensed and
discarded.

7. EVAPORATION DIFFERS FROM OTHER
OPERATIONS
1. Evaporation
VS
1. Drying
2. Distillation
3. Crystallization
4. Water distillation ( large scale evaporation)

8. EVAPORATOR;
• An evaporator is a device
used in a process to turn
the liquid form of a
chemical substance such
as water into its gaseous-
form/vapor.

9. COMPONENTS OF AN EVAPORATOR:
1. Thermoexpansion Valve (TEV):Meters refrigerant flow and converts
hot high pressure liquid to a cold low-pressure liquid.
2. Differential Pressure Switch: Monitors the cleanliness of the air filter
3. Evaporator Coil: Absorbs heat through the vaporization of low-pressure liquid.
4. Low-Pressure Cut Out Switch: Shuts off compressor when pressure drops
from 27.3 psi.
5. EMI Filter and EMI Gasket: Dissipates and prevents EMI from affecting the
operation of other electronic equipment located within close proximity.
6. Handle: Allows two people to lift evaporator assembly.
7. Terminal Board, Single Row: Allows for ease of troubleshooting and repair.
8. Condensate Drain Pan: Collects condensation from coil and discharges
through drain hole.
9. Evaporator Fan Motor: Drives evaporator housing fan.
10.Evaporator Fan Housing: Draws air across evaporator coil to increase

10. PROBLEMS
The practical solution of evaporation problems is profoundly effected by
character of the liquor is to be concentrated. It is the wide variation in liquor
characteristics which demands experience and judgement in designing and
evaporator . Some of the most important properties of the evaporatong liquid
are as follows.
1. Concentration: On evaporation the concentration of solution increases. The
density and viscosity increases with solid content until the liquor becomes
more viscous for adequate heat transfer. Continued boiling of saturated
solution causes crystals to form; these must be removed or the tubes clog.
2. Foaming: Some materials specially inorganic substances foam during evaporation.
A stable foam accompanies the vapour out of the evaporator, causing heavy
entertainment. In extreme cases the entire mass of the liquid may boil into vapour
outlet and be lost.

11. CONTINUE...
3. Temperature Sensitivity: Many fine chemicals, Pharmaceutical products,
foods are damaged when heated to moderate temperatures for relatively short
times. In concentrating such materials special techniques are needed to reduce
both the temperature of liquid and the time of heating.
4. Scale: Some solutions deposit scale on the heating surface. The overall
coefficient then diminishes until the evaporator may shut down and the tubes
cleaned. When the scale is hard and insoluble, the cleaning is difficult and
expensive.
5. Materials of construction: Whenever possible, evaporators are made of
some kind of steel.Many solutions, however, attack ferrous metals or
contaminated by them. Special materials such as copper, nickel, stainless steel,
aluminium, impervious graphite and lead are then used. Since these materials
are expensive, high heat transfer rates becomes specially desirable to minimize
the first cost of the equipment.

12. TYPES OF EVAPORATORS USED TODAY
The chief types of steam heated tubler evaporator in use today are;
1. Shell and tube type
• Long-tube vertical evaporator
a. Upward flow (Rising film evaporator)
b. Downward flow (Falling film evaporator)
c. Forced circulation
2. plate type
• Agitated-film evaporator

13. ALSO
• Flash evaporation
• Vacuum evaporation
• Centrifugal evaporator
• Rotary evaporator
• Vapor-compression evaporator
• Evaporative cooler
• Pumpable ice technology
• Circulation evaporator

14. A. UPWARD FLOW (RISING FILM
EVAPORATOR):
• The liquid being evaporated is feed from the
bottom into long tubes and heated with
steam condensing on the outside of the
tube from the shell side. This is to produce
steam and vapour within the tube bringing
the liquid inside to a boil. The vapour
produced then presses the liquid against
the walls of the tubes and causes the
ascending force of this liquid. As more
vapour is formed, the centre of the tube will
have a higher velocity which forces the
remaining liquid against the tube wall
forming a thin film which moves upwards.
This phenomenon of the rising film gives
the evaporator its name.

15. B. DOWNWARD FLOW
(FALLING FILM
EVAPORATOR):
• In falling film evaporators, the liquid product
usually enters the evaporator at the head of
the evaporator. In the head, the product is
evenly distributed into the heating tubes. The
liquid enters the heating tube and forms a thin
film on the tube wall where it flows
downwards at boiling temperature and is
partially evaporated. In most cases, steam is
used for heating the evaporator. The product
and the vapor both flow downwards in a
parallel flow. This gravity-induced downward
movement is increasingly augmented by the
co-current vapor flow. The separation of the
concentrated product from its vapor takes
place in the lower part of the heat exchanger

16. C. FORCED
CIRCULATION
• Developed for processing fluids which
are fouling, scaling, and crystallizing, The
raw material liquid is circulated through
circulation pump in the heating chamber
and separation chamber at a high speed
and heated up in the heating chamber
while flashed in the separation chamber,
to achieve efficient vapour-liquid
separation.
• The high flow speed of material liquid in
the heat exchange tube can improve heat
transfer efficiency. Evaporation process
takes place in the separator instead of
the heater. Therefore, the scaling caused
by crystallization and precipitation in the

17. AGITATED-FILM EVAPORATOR
• The feed enters evaporator at top, tangential to
shell and gets distributed along the shell by the
distributor. The rotor blades spread the feed
evenly on the heated surface into a thin film and
further agitate the film.
• Heating medium passing through the jacket
evaporates the volatile component in feed. The
vapor generated flow counter currently to feed
and gets cleared in entrainment separator
before leaving through vapor nozzle. The
concentrate product comes out at bottom.

18. PERFORMANCE OF EVAPORATOR
The principal measures of performance of a steam-
heated tubler evaporator are the capacity and the
economy of the evaporator.
• Capacity is defined as number of kilograms of water vaporized per hour.
• Economy is defined as number of kilograms of water vaporized per
kilogram of stream feed to the unit.
• Steam consumptionis defined as the ratio of capacity of evaporator
to the economy of evaporator (kilograms of steam per hour).

19. POTENTIAL HAZARDS
OF EVAPORATOR

20. ENVIRONMENTAL APPLICATIONS OF EVAPORATOR
1. Brine
2. Wastewater treatment
3. Manure
4. Sludge
5. By-product from bioethanol production
6. Food and agricultural waste
7. Fruit concentrate
8. Cement industries
9. Etc.