This is evaporation as used in pharmaceutics

1. EVAPORATION

2. CONTENT
• Definition of evaporation
• Key factors affecting process
• Principle
• Uses in concentration of solutions and other
advantages
• Single evaporator
• Multiple effect evaporator
• Pharmaceutical Case example

3. EVAPORATION
PROCESS
Definition
• Evaporation is a unit operation in pharmaceutics
where a liquid is partially vaporized by applying
heat to concentrate the solution or remove a
solvent.
Key factors affecting evaporation process include:
Temperature, Pressure, Surface area, solvent
properties and concentration of the solution.

4. PRINCIPLE OF EVAPORATION
• Evaporation is governed by the principle of heat transfer,
mass transfer and phase change.
How?
Heat is transferred by conduction through the metal wall
and convection within the liquid. The heating medium is
usually steam though metal wall into the liquid.
When the liquid molecules obtain latent heat of
vaporization, their kinetic energy gets sufficient enough to
overcome the intermolecular forces and escape into
vapor phase.

5. IMPORTANCES OF EVAPORATION
• USES IN CONCENTRATION OF SOLUTIONS
1. Concentration of Plant and Herbal Extracts.
Used in the manufacture of concentrated extracts for syrups, tinctures,
and liquid products by the removal of excess solvent.
2. Syrup Preparation.
Concentrates sugar solutions by evaporation to produce stable syrups
that are used as vehicles in many liquid oral dosage forms.
3. Antibiotics and Products of Fermentation. Concentration of fermentation
broths (e.g., penicillin, streptomycin)
before further purification or crystallization.

6. continuation
4. Bulk Drug Production. Reduces the volume of drug solutions, which
are then more readily
crystallized and purified into solid dosage forms.
5. Parenteral Product Formulation.
Concentration of injectable drug solutions to the required therapeutic
strength before sterilization.
6. Improvement of Stability and Shelf-life.
By elimination of water content, both microbial growth and hydrolytic
degradation are minimized in drug solutions.

7. 7. Crystallization. Super saturation of the API as
the solvent is driven out leads to crystal growth
of the API
8. Formulation of semisolid dosage forms to
achieve the desired consistency in ointments,
creams and emulsions.

8. Other importances include;
1. Prevention of degradation of a heat sensitive API
by evaporation at low pressure and temperature
2. Volume Reduction for Drying: Concentrating fruit
juice or a vaccine solution before it is fed into a
spray dryer to make a powder.
3. Solvent Recovery: Recovering ethanol,
isopropanol, or methanol from a reaction mixture.
4.Lyophilization

9. EQUIPMENTS USED IN EVAPORATION
PROCESS
 Evaporation equipments or machines are used in the
pharmaceutical industries to concentrate solutions by
evaporating the solvent (usually water)
 They include single evaporator and multiple effect evaporator
1. SINGLE EVAPORATOR
It is called single because it consists of one evaporator unit
operating independently (unlike multiple-effect evaporators
that have several units linked together).

10. SINGLE EVAPORATOR

11. Principle of Operation
The working principle is based on:
• Heat Transfer: Steam supplies heat to the
liquid feed.
• Phase Change: The solvent (water) absorbs
this heat and vaporizes.
• Separation: The vapor is separated from the
concentrated liquid (product).

12. Working Steps
1. Feed Entry: The dilute solution (drug + solvent) enters the
evaporator.
2. Heating: Steam is passed into a heating chamber (jacket or coil),
transferring heat to the solution.
3. Evaporation: The solvent evaporates due to heat, leaving a
concentrated solution.
4. Vapor Separation: The vapor is separated from the concentrated
liquid in a vapor space.
5. Condensation: The vapor passes into a condenser, where it is
cooled and collected as distillate (usually discarded or reused).
6. Product Withdrawal: The concentrated liquid is collected as the
final product.--

13. Advantages of single evaporator
• Simple in design and operation.
• Low initial cost compared to multiple-effect
evaporators.
• Easy cleaning and maintenance.
• Suitable for small-scale pharmaceutical
production.—

14. Disadvantages of single evaporator
• High steam consumption (not energy
efficient).
• Only suitable for small-scale operations.
• Not economical for large volumes.
• Limited temperature control . may degrade
heat-sensitive drugs.

15. MULTIPLE EFFECT EVAPORATOR

16. MULTIPLE EFFECT EVAPORATOR
• Description:
In a multiple-effect evaporator, several evaporator vessels are
connected in series. The vapor generated in one effect is used as
the heating medium for the next effect, thereby saving steam.
Principle of operation
• Principle of operation
A multiple-effect evaporator system utilizes the heat from steam
multiple times to evaporate liquid in a series of stage.

17. Construction and working
• Consists of two or more evaporator bodies,
connected in sequence.
• The first effect uses live steam directly. The
vapor produced in the first effect (at slightly
lower pressure and temperature) is used as the
heating medium in the second effect.
• The vapor from the second effect is used in the
third effect, and so on. The last effect’s vapor is
finally condensed in a condenser.

18. Feed can be introduced in three modes:
• Forward feed (feed enters the first effect, flows to the next).
• Backward feed (feed enters the last effect, flows backward).
• Mixed or parallel feed (variations depending on concentration
and heat sensitivity of product).

19. MULTIPLE EFFECT EVAPORATOR
Advantages
• Economical steam consumption
• Energy efficient for large-scale industries.
• Suitable for heat-sensitive materials when arranged
properly (like forward feed with vacuum)
Disadvantages
• Higher capital cost.
• More complex operation and maintenance.
• Larger space requirement.

20. HEAT ECONOMY
• Is the efficient use of thermal energy to drive
evaporation while minimizing energy waste.
E.g
• In multiple effect evaporators, the heat
economy is significantly higher than in single
effect evaporators because the latent heat of
vaporization is reused across multiple effects

21. Heat Economy Improvement Strategies:
1. Latent Heat of Evaporation: Amount of energy needed to convert a
liquid into a gas at its boiling point without a change in
temperature.
• Water = 2257 KJ/kg at 100°C
• Organic solvents (ethanol) = 855 KJ/kg
• Energy demand varies.
• Using water with high latent heat of evaporation improves heat
delivery to the evaporating machines compared to a liquid of lower
latent heat of evaporation
2. Heat Losses: Energy losses occur through convection, radiation,
conduction in evaporators. Insulated equipment and optimized
designs(minimizing surface area for heat loss) improve heat economy.

22. Continuation;
3.Heat Recovery: Systems like multiple effect evaporators/vapor
recompression recover and reuse heat.
• Multiple effect evaporators use vapor from one stage to heat the
next, reducing total energy consumption.
• Each effect operates at a lower pressure, allowing boiling at lower
temperatures, which is ideal for heat-sensitive pharmaceuticals.
4. Mechanical Vapor Recompression (MVR): MVR compresses vapor
to increase its temperature and pressure for heating, significantly
cutting energy use.
5. Process Integration: Heat integration (e.g., using waste heat from
other processes to preheat feed solutions) enhances overall energy
efficiency.

23. HEAT EFFICIENCY
• It’s a measure of the performance and
effectiveness of the evaporation process itself.
• How effectively the energy supplied is
transferred to the liquid for evaporation.
• It is often expressed as the ratio of the actual
amount of solvent evaporated to the
maximum theoretical amount that could be
evaporated by the energy input

24. Factors Affecting Efficiency:
• 1. Heat Transfer Rate: Efficiency is maximized by:
• High Heat Transfer Coefficients (U): Achieved by minimizing
scaling/fouling (which acts as an insulator), using agitated
thin-film evaporators for viscous products, and ensuring
turbulent flow.
• Large Heat Transfer Area (A): Larger surface area allows more
heat to pass from the steam to the product.
• High Temperature Difference (.T): A greater difference
between the heating steam temperature and the boiling
point of the solution drives heat transfer faster. However,

25. 2. Boiling Point Elevation (BPE): As the solution becomes more
concentrated, its boiling point rises. This reduces the effective temperature
difference (.T) between the heating medium and the solution, thus
reducing
the driving force for heat transfer and lowering efficiency. This is a
significant
challenge when concentrating syrupy pharmaceutical solutions.
3. Foaming and Entrainment: Foaming can cause valuable product to be
carried over (entrained) into the vapor stream and lost. This represents a
direct loss of product and a decrease in mass-based efficiency.
4. Heat Loss to Surroundings: Poorly insulated evaporators lose heat to the
environment, wasting energy and reducing efficiency.

26. CASE EXAMPLE: DURING ANTIBIOTIC
PRODUCTION OF PENICILLIN

27. How?
• After fermentation, the broth contains dilute
penicillin
• Solvent extraction separates penicillin into the
organic solvent e.g. amyl acetate
• Vacuum evaporation or use of multiple effect
evaporator is then applied to remove the solvent and
concentrate the crude antibiotic.

28. references
• Aulton’s pharmaceutics 5th
Edition
• Martin’s physical pharmacy and
pharmaceutics 7th
edition
END