Evaporation slide

Refer these slides to get evaporation knowledge in Pharmaceutical Engineering

1. Subject: PHARMACEUTICAL ENGINEERING-Theory Course code:BP304T PREPARED BY: KASHISH WILSON ASSISTANT PROFESSOR, MM SCHOOL OF PHARMACY, MM UNIVERSITY, SADOPUR, AMBALA

2. Contents: Objectives, applications and factors influencing evaporation Differences between evaporation and other heat process Principles, construction, working, uses, merits and demerits of 1. Steam jacketed kettle 2. Horizontal tube evaporator 3. Climbing film evaporator 4. Forced circulation evaporator 5. Multiple effect evaporator& Economy of multiple effect evaporator

3. WHAT IS EVAPORATION ? Evaporation is a type of phase transition. It is the process by which molecules in a liquid state (e.g water) spontaneously become gaseous (e.g water vapor). The equipment used for evaporation is known as Evaporator.

4. APPLICATION OF EVAPORATION MANUFACTURING OF BULK DRUGS MANUFACTURING OF BIOLOGICAL PRODUCTS MANUFACTURING OF FOOD PRODUCTS MANUFACTURING OF DE MINERALISED WATER

5. Factors affecting evaporation Temperature: Higher the temperature greater will be the evaporation. Vapor pressure: Rate of evaporation is directly proportional to the vapor pressure of the liquid. Lower the pressure ,greater will be the evaporation. Surface area: Greater the surface area of the liquid, greater will be the evaporation. Time of evaporation: Exposure time is longer, more will be the evaporation. Density: The higher the density, slower the liquid evaporates.

6. Differences between evaporation and other heat process Evaporation The residue obtained is concentrated liquid. Evaporating liquid is only one component. No attempt is made to separate the mixture of vapour The main purpose of this process is to get concentrated liquid only, but not to get crystals Other heat process Drying: the residue is solid Distillation: Evaporating liquid is combination of two or more components. Distillation: Seperation of two components is necessary. Crystallization:Concentrated product is in crystal form.

7. Continue: Concentration: Low concentration of the substance, faster the evaporation. Film and deposits: Some solutions deposit solid materials called scale on the heating surfaces. results in the overall heat-transfer coefficient decreases and evaporator must be cleaned. Foaming or frothing: food solution such as skim milk and some fatty-acid solution form a foam or froth during boiling. Economic factors: The recovery of solvent and utilization of waste heat are also important as they involves considerable reduction of cost.

8. TYPES OF EVAPORATION EQUIPMENT Open kettle or pan Horizontal-tube natural circulation evaporator Vertical-type natural circulation evaporator Long-tube vertical-type evaporator Falling-film-type evaporator Forced-circulation-type evaporator

9. OPEN KETTLE OR STEAM JACKETED EVAPORATOR

10. Continue: Steam is supplied to the jacketed kettle in which the aqueous extract is placed. Heat is transferred to the extract by conduction and convection. CONSTRUCTION Copper is the excellent material for the kettle because of its conductivity. Iron is used for construction of jackets since it has minimum conductivity.

11. Continue WORKING Aqueous extract to be evaporated is placed in the kettle. Steam is supplied through inlet. Steam gives out its heat to the contents and the condensates leaves through the outlet. ADVANTAGES 1. Used for both small scale & large scale operation. 2. Simple in construction and easy to operate. 3. Low maintenance & installation cost. 4. Wide variety of materials.

12. Continue: DISADVANTAGE 1.Heat economy is less. 2. Not suitable for heat sensitive materials. 3. Heat decreases on product concentration. 4. Since, open type so vapor passes to atmosphere USES Concentrating aqueous and thermo-stable liquors. Eg. Cooking pickels, liquorice extract etc.

13. (a) HORIZONTAL TUBE TYPE / (b) VERTICAL TUBE TYPE EVAPORATOR

14. HORIZONTAL TUBE EVAPORATOR Principle: Steam is passed through the horizontal tubes, which are immersed in a pool of liquid to be evaporated. Heat transfers through the tubes and the solvent evaporates. Concentrated liquid is collected. CONSTRUCTION: Large cylindrical body with doomed shaped at the top and bottom, made of cast iron or plate steel. Stainless steel tubes are used in steam compartments. WORKING: Feed is introduced into the evaporator until the steam compartment is immersed. The horizontal tubes receives the heat and conduct it to the liquid. The feed absorbes heat and solvent gets evaporated. Concentrated liquid is collected. USES: Best suited for non-viscous solution. E.g. Cascara extract.

15. VERTICAL TUBE EVAPORATOR Principle: Liquid is passed throgh the vertical tubes and steam is suppliedfrom outside tubes. Heat transfer takes place through the tubes and the liquids inside tube gets heated. The solvent evaporates, vapor escapes from the top and concentrated liquid is collected from bottom. CONSTRUCTION:Consist of long cylindrical body made up of cast iron with domeshaped top and bottom. Calandria are fitted at the bottom. Calandria consist of number of vertical tubes with diameter 0.05-0.075 meters & length of 1-2 meters.About 100 such tubes are fitted in the body of 2.5 mtr. Inlets are provided for steam and feed. Outlets are provided for vapor, concentrated products, non-condensed gases and condensate.

16. Continue: ADVANTAGES 1. Increases the heating surface 10-15 times than steam jacketed kettle. 2. Vigorous circulation enhances rate of heat transfer. 3. More units can be joined. DISADVANTAGES 1. Liquid to be maintained above calandria. 2. Complicated- increased installation cost. 3. Pressure has to maintain. 4. Cleaning and maintenance is difficult. USES Manufacture of cascara extract, sugar, salt, caustic soda etc.

17. CLIMBING FILM EVAPORATOR ( RISING FILM EVAPORATOR )

18. Continue: Principle: Tubes are heated externally by steam. Thepreheated feed enters from the bottom and flows up through the the heated tubes. Liquid near walls becomes vapour and forms small bubbles. Larger bubbles flow up with slug and strikes deflector. Deflector throws the concentrate, down to the bottom. CONSTRUCTION Heating unit consists of steam jacketed tubes. Long and narrow tubes are held between the plates. Deflector is placed at the top of the vapour headInlets are provided for steam and feed. Outlets are provided for vapour, concentrated product, non condensed gases and condensate.

19. Continue: ADVANTAGES 1. Large area for heat transfer 2. Enhanced heat transfer 3. Suitable for heat sensitive materials 4. Used for foam formingliquids 5. Instrument needs less space Uses: Insulin, liver extracts, vitamins, foaming liquids, corrosivesolutions can be concentrated DISADVANTAGES 1. Expensive, construction is quite complicated 2. Cleaning and maintenance is quite difficult 3. Large head space required 4. Not for viscous, salting and scaling liquids

20. FORCED CIRCULATION EVAPORATOR

21. Continue: Principle: Liquid is circulated through the tubes at high pressure by means of pump. Hence boiling does not takes place as boiling point is elevated. Forced circulation creates agitation. When liquid leaves the tube and enters the vapour head, pressure falls suddenly. This leads to flashing of superheated liquor. Thus evaporation is effected. CONSTRUCTION: Heating unit consists of steam jacketed tubes. Inlets are provided for steam and feed. Outlets are provided for vapour, concentrated products, non condensed gases and condensate. Pump is connected near the inlet.

22. Continue: ADVANTAGES 1. Heat transfer coefficient is high 2. Salting, scaling are not possible 3. Suitable for high viscous preparations USES 1. Insulin and liver extract 2. Crystallizing operations DISADVANTAGES 1. Equipment is expensive 2. More power supply is required

23. Multiple Effect Evaporator

24. Continue: Vertical tube evaporators are connected in several ways as to achieve large scale evaporation as well as great economy. Construction: It consists of three evaporators joined together, vapour from first evaporator acts as heating medium for 2 nd evaporator and second for third, last evaporator is connected to vaccum pump. Working: If the feed to the first effect is near the boiling point at the pressure in the first effect, 1 kg of steam will evaporate almost 1 kg of water The first effect operates at a temperature that is high enough that the evaporated water serves as the heating medium to the second effect Here, again, almost another kg of water is evaporated, which can then be used as the heating medium to the third effect

25. Continue: As a very rough approximation, almost 3 kg of water will be evaporated for 1 kg of steam in a three-effect evaporator Hence, the steam economy, which is kg vapor evaporated/kg steam used, is increased This also holds approximately for more than three effects However, the increased steam economy of a multiple-effect evaporator is gained at the expense of the original first cost of these evaporators Advantages: It is suitable for large and continuous operation, highly economical and 5 evaporators gets attached to it.

26. Economy of multiple effect evaporator The economy of an evaporator is quantity of vapour produced per unit steam admitted. The economy is expressed by Economy= Total mass of vapour produced Total mass of steam supplied In single effect evaporator, steam produces vapour only once where as in multiple effect evaporator steam produces vapour many times depending on numbers of evaporato r connected.

27. Thank You