CH- 4 Evaporation

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Evaporation

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Slide1:

EVAPORATION By Mr. V. D. Ramani Assistant Professor Sumandeep Vidyapith University Vadodara

Topics to be covered….:

Definition Mechanism & Basic concept Factor affecting evaporation Evaporators Topics to be covered….

Definition:

‘The removal of liquid from a solution by vaporization below its boiling point of the solution in a suitable vessel and, leaving a concentrated liquid residue.’ Definition

Mechanism:

When heat applied in solution the motion of molecules increase and molecules present in the surface overcome the surface tension of the liquid and it evaporates because surface molecules have less cohesive force than others. Mechanism Evaporation

????:

Why do you feel chilly when getting out of a swimming pool? Fast molecules escape the liquid, taking energy, and leaving the liquid cooler. Evaporation is a cooling process! Wrap a wet cloth around a container to cool it off at a picnic. ????

Mechanism:

Boiling is a cooling process Temperature is 100 degrees C no matter how much heat we give the water. Water boils as fast as it is being warmed by heating. The steam carries away the heat. Mechanism Boiling

Mechanism:

Condensation generally occurs in the atmosphere when warm air rises, cools and looses its capacity to hold water vapor. As a result, excess water vapor condenses to form cloud droplets. Mechanism Condensation

???:

Why does a cold drink get wet on the outside? What causes Dew, fog, clouds? ???

Mechanism:

Mechanism

Mechanism:

Mechanism

Factors Affecting Evaporaton:

Rate of Evaporation Factors Affecting Evaporaton Where, M = Rate of Evaporation ( m 3 /s ) S = Surface area of liquid exposed to atmosphere ( m 2 ) P = Atmospheric pressure ( kPa ) b = Max vapor pressure at temperature of Air ( kPa ) b’= Pressure due to vapor of Liquid, actually present in air ( kPa ) K = Constant ( m/s )

Factors Affecting Evaporaton:

Following factors affects evaporation. 1) Temperature 2) Surface area 3) Conviction (Agitation) 4) Max vapor pressure at temperature of Air 5) Atmospheric pressure on the liquid under evaporation 6) Type of product required 7) Economic factors Factors Affecting Evaporaton

Factors Affecting Evaporaton:

Temperature The rate of evaporation is directly proportional to the temperature. Factors Affecting Evaporaton

Factors Affecting Evaporaton:

Surface area The rate of evaporation is directly proportional to the surface area of the vessel exposed to evaporation Factors Affecting Evaporaton

Factors Affecting Evaporaton:

Conviction (Agitation) Conviction (Agitation) radiate the heat from surface of liquid and decreases the vapor to gets saturated thus increase the vaporization. Factors Affecting Evaporaton

Factors Affecting Evaporaton:

Pressure Pressure inversely proportional to vaporization of liquid Factors Affecting Evaporaton

Factors Affecting Evaporaton:

Pressure Max vapor pressure at temperature of Air Liquid with lower boiling point evaporates fast due to High vapor pressure at low temperature (b) Atmospheric pressure on the liquid under evaporation If the outer atmosphere is dry the value of b’ is low and hence greater the evaporation. Factors Affecting Evaporaton

Factors Affecting Evaporaton:

Type of product required Open Pan Evaporator gives liquid concentrates. Spray drying gives dry powder with good solubility Vacuum drying gives product suitable for preparation of granules. Factors Affecting Evaporaton

Factors Affecting Evaporaton:

Economic factors Its important to calculate cost of evaporation process Labor, Fuel, Floor space, Recovery of solvent, Utilization of waste heat Needs to be taken in to consideration Factors Affecting Evaporaton

MCQ:

1. To say that evaporation is a cooling process is to say that the A) the less energetic particles escape. B) more energetic particles escape. C) more energetic particles remain in the water. 2. When a gas is changed to a liquid state, the gas A) absorbs energy. B) releases energy. C) neither releases nor absorbs energy. D) both releases and absorbs energy. 3. On a humid day, water condenses on the outside of a glass of ice water. This phenomenon occurs mainly because of A) capillary action. B) adhesion of water molecules to glass. C) evaporation. D) the saturation of cooled air. E) the porosity of glass. 4. When a block of ice at zero degrees Celsius melts, the ice A) absorbs energy from its environment. B) releases energy and gets warmer. C) absorbs energy and gets warmer. D) releases energy to its environment. E) absorbs energy but does not change its temperature. 5. Unit operations are performed to make chemical changes in product A) Yes B) No MCQ

Types of Evaporators:

A) Pan Evaporator a) Evaporating Pan b) Evaporating still B) Tubular Evaporator a) Short Tube i) Horizontal Short Tube Evaporator ii) Vertical Short Tube Evaporator 1. Standard Type 2. Basket Type iii) Short Tube with Multiple effect 1. Parallel Flow 2. Forward flow 3. Backward flow 4. Combined flow b) Long Tube Evaporator i ) Climbing film Evaporator ii) Falling film evaporator iii) Forced circulation evaporator C) Wiped Film Evaporator D) Centrifugal Rotary Evaporator Types of Evaporators

A) Pan Evaporator a) Evaporating Pan (Steam Jacketed kettle ):

A) Pan Evaporator a) Evaporating Pan ( Steam Jacketed kettle )

A) Pan Evaporator (Steam Jacketed kettle ):

A) Pan Evaporator ( Steam Jacketed kettle ) Principle: it is also a natural circulating evaporator Steam is supplied to Jacketed kettle in which liquid extract is placed Steam gives out heat to kettle The steam heat transferred to aqueous extract by Conduction and convection As temperature raises solvent molecule present at surface starts vaporizing As temperature raises vaporization increases Construction: Hemispherical structure consist of inner pan called kettle Kettle is enveloped with outer pan called Jacket The two pan are joined to enclose a space thorough which steam is passed Material of construction is Copper, Tinned Copper(For Acidic extract), Tinned Iron. Jacket consist of Inlet and outlet for non-condensed steam at the top Condensed steam removed through outlet provided at the bottom The kettle is provided with one outlet for product discharge at the bottom

A) Pan Evaporator (Steam Jacketed kettle ):

A) Pan Evaporator ( Steam Jacketed kettle ) Working: Place the aqueous extract to kettle Steam supplied through Inlet Steam gives out heat to content and condensate leaves through outlet Content must be stirred manually or mechanically Rate of evaporation is fast initially and gradually slower down as extract became concentrated Operation must carried out in well ventilated place. On completion product is removed through outlet present at bottom or by tilting the kettle. Advantages Disadvantages Can be constructed for small scale and large scale operations. Heat economy is less. Hence cost per unit material production is more. Easy to operate, clean & maintain. Not suitable for heat sensitive materials. Installation cost is low. Heating area decreases as the product becomes more and more concentrated Wide variety of materials can be used for construction. Saturation of the atmosphere with vapours can take place which can decrease the rate of evaporation. Stirring of the contents and removal of products is simple . Cannot be used for organic inflammable solvent as there are chances of fire.

A) Pan Evaporator b) Evaporating Still With Condenser (Extention of Pna Evaporators) :

A) Pan Evaporator b) Evaporating Still With Condenser ( Extention of Pna Evaporators)

A) Pan Evaporator Evaporating Still With Condenser (Extention of Pna Evaporators) :

A) Pan Evaporator Evaporating Still With Condenser ( Extention of Pna Evaporators) Principle: It has the same principle as that of an evaporating pan. Thus it is also a natural circulating evaporator Construction & Working: It is similar to evaporating Pan It consists of jacket and shallower pan with cover. Cover is connected to a condenser so that the liquid is distilled off and collected in the receiver. A tube fitted with a tap is connected at the lowest end so that the product can be removed. Copper and stainless steel are generally used as the materials of constructions. Advantages Disadvantages As vapour is condensed, it increases the rate of evaporation. Heating surface is limited. Easy to operate, clean & maintain. It can be used for aqueous and organic solvents. Wide variety of materials can be used for construction.

B) Tubular Evaporator a) Short Tube Evaporators i) Horizontal short Tube Evaporator:

B) Tubular Evaporator a) Short Tube Evaporators i) Horizontal short Tube Evaporator

B) Tubular Evaporator a) Short Tube Evaporators i) Horizontal short Tube Evaporator:

B) Tubular Evaporator a) Short Tube Evaporators i ) Horizontal short Tube Evaporator Principle: It is based on the principle of natural circulation. Steam is passed through horizontal tube of evaporator which is immersed in pool of liquid to be evaporated. Heat transfer takes place through the tubes and liquid I pool The solvent evaporates and escape from topside of evaporator The concentrated liquid collected from bottom Construction: It consist of large cylindrical body with conical or dome shaped top & bottom Made-up of cast iron or plate steel Avg diameter : 1.8 to 2.4 meter, Avg Height : 2.4 to 3.6 mtr Lower part consist of steam compartment (Half of the body of cylindrical body)with Inlet and vent outlet for steam opposite side to each other Condenses outlet present at the bottom of steam compartment Steam compartment consist of 6-8 SS horizontal tubes

B) Tubular Evaporator a) Short Tube Evaporators i) Horizontal short Tube Evaporator:

B) Tubular Evaporator a) Short Tube Evaporators i ) Horizontal short Tube Evaporator Working Feed is introduced in to evaporator up to steam compartment is satisfactory immersed Steam is introduced to steam compartment Heat transfer takes place through the tubes and liquid I pool due to temperature gradient and gets evaporated Steam condensate passes through corresponding outlet Vapor than escapes through the outlet placed at the top This process continued until thick liquid is form which can collected from the bottom outlet. Advantages Cost of operation is low Efficiently utilization of heat Easy to construct and maintain Stirring and removal of product is easy Disadvantages: Difficult to clean Not suitable for thermolebile material Cost of installation and maintenance is high Application: Suitable for Non Viscous liquid that do not deposit scale or crystal on evaporation ( example: Cascura extract)

B) Tubular Evaporator a) Short Tube Evaporators i) Vertical short Tube Evaporator (Standard Type):

B) Tubular Evaporator a) Short Tube Evaporators i ) Vertical short Tube Evaporator ( Standard Type ) Principle: It is based on the principle of natural circulation.

B) Tubular Evaporator a) Short Tube Evaporators i) Vertical short Tube Evaporator (Standard type):

B) Tubular Evaporator a) Short Tube Evaporators i ) Vertical short Tube Evaporator (Standard type) Construction: As the area of the evaporator increases, the external steam jacket is not sufficient. Here liquor carrying tubes are heated externally by the steam chest. Lower portion of the evaporator consists of a nest of tubes with(1000) with liquor inside and the steam outside. This part of the evaporator is known as CALANDRIA. The liquor is maintained at a level slightly above the top of the tubes. As the liquor boils, it shoots up through the tubes and returns back through the central down take. The heat is transferred from the steam to the liquid to be heated. The liquid thus boils. Boiling liquid rises up through the smaller tubes of the calandria and returns through the central down take.

B) Tubular Evaporator a) Short Tube Evaporators i) Vertical short Tube Evaporator (Standard type):

B) Tubular Evaporator a) Short Tube Evaporators i ) Vertical short Tube Evaporator (Standard type) Advantages Disadvantages Mare heating surface area. Liquor is heated for a long time so there chances of thermal decomposition Rate of heat transfer is good because no film is formed. Expensive Low Head room Difficult to clean as tubes are difficult to replace Complex design. Thus can be used for only one product. Applications: Used for solution carrying solids Not for foamy Liquids For concentration of extract. For sugar industry For Salts.

B) Tubular Evaporator a) Short Tube Evaporators ii) Vertical short Tube Evaporator (Basket type):

B) Tubular Evaporator a) Short Tube Evaporators ii) Vertical short Tube Evaporator (Basket type) Vs

B) Tubular Evaporator a) Short Tube Evaporators ii) Vertical short Tube Evaporator (Basket type):

B) Tubular Evaporator a) Short Tube Evaporators ii) Vertical short Tube Evaporator (Basket type) Construction: In this evaporator, the steam is outside the tubes and the liquid is inside the tubes. Entire heating element is a single unit & evaporator has a conical bottom. The tubes are placed close together to form a smaller unit in diameter than evaporator body. There is no central down take but the annular space becomes the down take. Liquid boils up the tubes which and recalculates downwards through the annular space between the basket and wall of the evaporator. Applications: For sugar , Salts and Heavy chemicals.

B) Tubular Evaporator a) Short Tube Evaporators iii) Short Tube Evaporator with Multiple effect :

B) Tubular Evaporator a) Short Tube Evaporators iii) Short Tube Evaporator with Multiple effect

B) Tubular Evaporator a) Short Tube Evaporators iii) Short Tube Evaporator with Multiple effect :

B) Tubular Evaporator a) Short Tube Evaporators iii) Short Tube Evaporator with Multiple effect In single effect evaporator: S team heat >>>> liquids >>> provides the latent ( Concealed) heat of vaporization >>> vapors are condensed in the condenser >>>> latent heat to the cooling water >>>> it goes to waste . To avoid this wastage two evaporators are connected together with the piping arrangement so that the vapor from the calandria of the first effect is used to heat the calandria of the second effect . This means that the calandria of the second effect is used as a condenser for the first time. So that the latent heat of vaporization is used to evaporate more quantity of the liquid instead of its going as waste. The vapor from the second effect then taken to a condenser and converted in to the liquids In general not more than Three or four effects are combined together to have economical and efficient evaporation of liquids

B) Tubular Evaporator a) Short Tube Evaporators iii) Short Tube Evaporator with Multiple effect :

B) Tubular Evaporator a) Short Tube Evaporators iii) Short Tube Evaporator with Multiple effect In the beginning the equipment is at room temperature and the atmospheric pressure. The liquids feed is introduced to all the three evaporators up to the level of the upper tube sheets. The vent valves V1, V2, V3 and V4 are kept open and all other valves are closed. Now a high vacuum is created in the liquids chambers of evaporators. The steam valves S1 and condensate valves are opened. Steam is supplied. Steam first replaces cold air in the steam space of 1^st evaporator. When all the cold air is removed the valves V1 is closed. The supply of steam is continued until the desired pressure P0 is created in the steam space of 1^st evaporator. At this pressure the temperature of the steam is t0. Steam gives its temperature to the liquids feed in the 1 st evaporators and gets condensed. Condensate is removed through the valve C1. Due to the heat transfer the liquids temperature increases and reaches the boiling point. During this process vapor will be generated from the liquid feed. So formed vapor displaces air in the upper part of 1^st evaporator. Move rover the vapor also displaces the air in the steam space of the 2^nd evaporator. After complete displacement of air by vapor in the steam compartments of 2^nd evaporator the valves V2 is closed. The vapor of 1^st evaporator transmit its heat to its liquids of the 2^nd evaporators and gets condensed, condensate is removed through the valve C2. These steps continue in the 3^rd , 4th evaporator also.

B) Tubular Evaporator a) Short Tube Evaporators iii) Short Tube Evaporator with Multiple effect :

B) Tubular Evaporator a) Short Tube Evaporators iii) Short Tube Evaporator with Multiple effect Now the products valves are opened to collect the thick liquid Variants of Multiple effect evaporators Continuous supply of fed ( Parallel flow) In this evaporator there is a continuous supply of feed continuous supply of steam and continuous withdrawal of liquid from all the three evaporators. Hence the evaporators works continuously with all the temperature and pressure in balance. Forward feed method , In the forward feed method the mother liquor is introduced in to 1^st then transferred to 2^nd and then to 3^rd , 4th. Backward fed method the mother liquior is introduced in to the 4th evaporator, then transferred to 3^nd, 4th then transferred to 1^st . Mixed feed method(Combination flow) , the mother liquor is introduced in to 2^nd and 3 rd evaporators then transferred to 4^rd evaporators and then transferred to 1^st evaporator.

B) Tubular Evaporator a) Short Tube Evaporators iii) Short Tube Evaporator with Multiple effect :

B) Tubular Evaporator a) Short Tube Evaporators iii) Short Tube Evaporator with Multiple effect

B) Tubular Evaporator a) Short Tube Evaporators iii) Short Tube Evaporator with Multiple effect :

B) Tubular Evaporator a) Short Tube Evaporators iii) Short Tube Evaporator with Multiple effect

B) Tubular Evaporator a) Short Tube Evaporators iii) Short Tube Evaporator with Multiple effect :

B) Tubular Evaporator a) Short Tube Evaporators iii) Short Tube Evaporator with Multiple effect

B) Tubular Evaporator a) Short Tube Evaporators iii) Short Tube Evaporator with Multiple effect :

B) Tubular Evaporator a) Short Tube Evaporators iii) Short Tube Evaporator with Multiple effect

B) Tubular Evaporator a) Short Tube Evaporators iii) Short Tube Evaporator with Multiple effect :

B) Tubular Evaporator a) Short Tube Evaporators iii) Short Tube Evaporator with Multiple effect V1 V4 V2 V3 C1 C1 C2 C2 C3 C3 C4 C4 S1 S2 S3 S4 P1 P2 P3 P4

B) Tubular Evaporator a) Short Tube Evaporators iii) Short Tube Evaporator with Multiple effect :

B) Tubular Evaporator a) Short Tube Evaporators iii) Short Tube Evaporator with Multiple effect Advantages Disadvantages Suitable large scale and continuous operation Expensive & complex construction Highly economical when compared with single effect. Difficult to clean and maintain About 3 to 4 evaporators can be attached Large flour space is required. Not suitable for suspensions

B) Tubular Evaporator b)Long Tube Evaporator i) Climbing film Evaporator :

B) Tubular Evaporator b)Long Tube Evaporator i ) Climbing film Evaporator

B) Tubular Evaporator b) Long Tube Evaporator i) Climbing film Evaporator :

B) Tubular Evaporator b) Long Tube Evaporator i ) Climbing film Evaporator Principle: It is based on the principle of natural circulation with climbing film. In climbing film evaporators, tubes are heated externally or by steam. The Preheated feed enters the bottom and flows up through the heated tubes. Thus rapid heating takes place due to enhanced overall coefficient of the preheated feed. The liquid near the wall becomes vapour and forms small bubbles. The small bubbles tend to fuse to form larger bubbles along with the entrapped slug. The liquid films are blown up from the top of the tubes and strikes the entrainment separator .

B) Tubular Evaporator b) Long Tube Evaporator i) Climbing film Evaporator :

B) Tubular Evaporator b) Long Tube Evaporator i ) Climbing film Evaporator 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 vapor head. Inlets are provided for steam and feed. Outlets are provided for vapor, concentrated product, non condensed gases and condensate. Working: Preheated liquid feed is introduced from bottom. Steam enters in to space outside the tube through inlet. Heat is transferred through walls of tube to liquid. Liquid became vapor and form small bubbles. Small bubbles merge with each other and became bigger. This big bubble travels upward through tubes with trapped liquid within it. Which facilitate as thin film of liquid on inner surface of tube. Liquid gets vaporized rapidly Deflector berks down the foam formation and release the vapor in bubble. Vapor collected in condenser and

B) Tubular Evaporator b) Long Tube Evaporator i) Climbing film Evaporator :

B) Tubular Evaporator b) Long Tube Evaporator i ) Climbing film Evaporator Advantages Disadvantages Large area for heat transfer is provided. Expensive & complex construction As liquid flows at a high velocity, resistance for heat transfer at the boundary layers is reduced. Difficult to clean and maintain The time of contact between the liquor and heating surface is short. Thus it is suitable for heat sensitive materials Large head space is required. Suitable for foam forming liquids as foam can be broken in an entrainment Deflector. Not advisable for scaling liquids and viscous liquids Requires low floor space.

B) Tubular Evaporator b) Long Tube Evaporator ii) Falling film evaporator :

B) Tubular Evaporator b) Long Tube Evaporator ii) Falling film evaporator

B) Tubular Evaporator b) Long Tube Evaporator ii) Falling film evaporator :

B) Tubular Evaporator b) Long Tube Evaporator ii) Falling film evaporator Principle: It is based on the principle of natural circulation with Falling film. They tend to form layers of bubbles which travel down the tubes. Concentration takes place during this downward journey and vapor and liquid are separated at the bottom.

B) Tubular Evaporator b) Long Tube Evaporator ii) Falling film evaporator :

B) Tubular Evaporator b) Long Tube Evaporator ii) Falling film evaporator Advantages Disadvantages Suitable for highly viscous liquids Expensive & complex construction Liquid is not overheated Difficult to clean and maintain Highly acidic and corrosive feeds can be concentrated. Not suitable for suspensions

B) Tubular Evaporator b) Long Tube Evaporator iii) Forced circulation evaporator:

B) Tubular Evaporator b) Long Tube Evaporator iii) Forced circulation evaporator

B) Tubular Evaporator b) Long Tube Evaporator iii) Forced circulation evaporator:

B) Tubular Evaporator b) Long Tube Evaporator iii) Forced circulation evaporator Heating Element Vapour Head Liquor Return Pipe Circulating Pump Deflector

B) Tubular Evaporator b) Long Tube Evaporator iii) Forced circulation evaporator:

B) Tubular Evaporator b) Long Tube Evaporator iii) Forced circulation evaporator Basically, these have natural circulation with mechanical agitator. Higher coefficients of heat transfer are obtained in forced-circulation evaporators. In these types of evaporators, a centrifugal pump forces liquid through the tubes at an entering velocity of 2 to 5.5m/s The tubes are longer and narrower than in the standard vertical evaporator. Principle & Working: Based on Forced circulation with rapid agitation. In forced circulation evaporators, liquid is circulated through tubes at high pressures by the means of a pump. Hence boiling does not take place as the boiling point is elevated. Forced circulation also creates some form of agitation. When the liquid enters the vapour head and enters the vapour head, pressure falls suddenly. This leads to the flashing of super heated liquor which leads to evaporation.

B) Tubular Evaporator b) Long Tube Evaporator iii) Forced circulation evaporator:

B) Tubular Evaporator b) Long Tube Evaporator iii) Forced circulation evaporator Advantages Disadvantages Rapid Liquid movement improves uniform heat transfer. High cost, power is required for circulating pumps. Positive circulation. Residence time is more. Can be operated under reduced pressure. Therefore suitable for thermo labile materials. Considerable head room is required Ideal for Viscous liquid Less chances of solid deposition in tubes

C) Wiped Film Evaporator:

C) Wiped Film Evaporator

C) Wiped Film Evaporator:

C) Wiped Film Evaporator Principle : Works on principal of wiped film Construction and working : Vertical cylinder body is enveloped in side the steam jacket. Center shaft consisting of wiper blades placed in side the vertical cylinder body of evaporator. Shaft is attached with motor at the top. Wiper blades are arranged with 0.75 -4 mm distance from the wall of cylindrical body. Feed is introduced wile motor is on at 200-300 RPM from the inlet present at the top. Steam is introduced though the steam inlet and vent is opened. Fast Rotating wipers spreads the feed uniformly on the hot inner surface of cylinder. Vapors produces flow counter currently into the upward direction on heating surface. The concentrated solution is drawn off at the bottom of evaporator. It can handle solution with viscosity up to 3000 centipoise . Residence time is 5 – 25 sec.

C) Wiped Film Evaporator:

C) Wiped Film Evaporator Advantages Disadvantages Rapid Liquid movement improves uniform heat transfer. High cost, power is required for rotating shaft. Ideal for Viscous liquid (up to 3000 Cp) High maintenance Less chances of solid deposition in evaporator Difficult in cleaning Residence time is less( 5 -25 sec).

D) Centrifugal Rotary Evaporator:

D) Centrifugal Rotary Evaporator

D) Centrifugal Rotary Evaporator:

D) Centrifugal Rotary Evaporator Principle : Works on principal of film formation by centrifugal force. Construction and working : Inner smooth surfaced Bowl shaped body is fixed in steam box. Center shaft attached at bottom of Bowl. Shaft is attached with motor at the Bottom. Feed is introduced from the top to middle of bowl wile motor is on at 400-1600 RPM. Steam is introduced in the steam box and vent is opened. Fast Rotating bowl spreads the feed uniformly on the hot inner surface of bowl. Centrifugal force produces flow counter currently into the upward direction on heating surface. The concentrated solution is drawn off from the collection tubes at the top. Residence time is 1 – 2 sec.

D) Centrifugal Rotary Evaporator:

D) Centrifugal Rotary Evaporator Advantages Disadvantages Rapid Liquid movement improves uniform heat transfer Power is required for rotating shaft Easy to cleaning Not Ideal for Viscous liquid Less chances of solid deposition in evaporator Residence time is less( 1-2 sec) Low maintenance

MCQ:

1) Pan evaporator works on _______Principle a) Forced circulation b) Natural Circulation c) Falling film with forced circulation d) All above 2) Evaporating Still is better than Pan Evaporator Because … i) Effective utilization of energy ii) Solvent recovery efficacy iii) Economic in installation iv) Easy to clean a) i & ii b) i & iii c) iii & iv d) i & iv 3) Which element have highest heat conduction capacity a) Cast Iren b) Copper c) Stainless Steel 4) Best suitable evaporator for viscous liquid. a) Vertical short Tube Evaporator (Basket type) b) Climbing film Evaporator c) Wiped Film Evaporator d) Evaporating Still With Condenser MCQ

MCQ:

5) Identify the following evaporator. a) Multiple effect with forward flow b) Multiple effect with backward flow c) Multiple effect with parallel flow d) Multiple effect with combination flow MCQ

MCQ:

6) Identify the following evaporator. a) Centrifugal Rotary Evaporator b) Climbing film Evaporator c) Wiped Film Evaporator d) Forced circulation evaporator MCQ

MCQ:

7) Lower portion of the evaporator consists of a nest of tubes called…. a) Basket b) Calendria c) Jacket d) Vent 8) Series of Liquid transport in Multiple effect evaporator with forward flow is… a) Evaporator 1 >> Evaporator 3 >> Evaporator 2 b) Evaporator 2 >> Evaporator 1 >> Evaporator 3 c) Evaporator 2>> Evaporator 3 >> Evaporator 1 d) Evaporator 1 >> Evaporator 2 >> Evaporator 3 9) As the Vapor pressure of liquid increases, the rate of evaporation….. a) Increases b) Decreases c) Remains constant d) Initially Increases than decreases 10) Best suitable evaporator for viscous liquid. a) Vertical short Tube Evaporator (Basket type) b) Climbing film Evaporator c) Wiped Film Evaporator d) Evaporating Still With Condenser MCQ

MCQ:

11) Cyclone separator is used in Forced circulating evaporator to…. a) To reduce the head pressure b) To separate vapor from bulk liquid c) To separate solider particles from bulk liquid d) Non of the above 12) Economy of evaporator is considered based upon… a) Maximum utilization of heat applied b) Maximum output with minimum utilization of energy c) Minimum loss of energy during operation d) All the above 13) Equation for rate of evaporation a) M ∝ P/A(b-b’) b) M ∝ A/P(b-b’) c) M ∝ A/P(b’-b) d) M ∝ P/A(b’-b) 14) In Equation for rate of evaporation b stands for…. a) Steam pressure b) Vapor pressure of liquid c) Vapor pressure of surround air d) Atmospheric pressure MCQ

MCQ:

15) Identify the following evaporator. a) Centrifugal Rotary Evaporator b) Climbing film Evaporator c) Wiped Film Evaporator d) Forced circulation evaporator MCQ

MCQ:

16) Function of deflector in forced circulating evaporator a) To reduce the head pressure b) To separate vapor from bulk liquid c) To separate solider particles from bulk liquid d) To break down the foam 17) Major drawback of shortage evaporator compared to Long tube evaporator is.. a) Low contact time b) Low heat transfer to liquid bulk c) Low product output d) All the above 18) Series of Liquid transport in Multiple effect evaporator with combination flow is… a) Evaporator 1 >> Evaporator 3 >> Evaporator 2 b) Evaporator 2 >> Evaporator 1 >> Evaporator 3 c) Evaporator 2>> Evaporator 3 >> Evaporator 1 d) Evaporator 3 >> Evaporator 1 >> Evaporator 2 19) Series of Liquid transport in Multiple effect evaporator with Backward flow is… a) Evaporator 1 >> Evaporator 3 >> Evaporator 2 b) Evaporator 2 >> Evaporator 1 >> Evaporator 3 c) Evaporator 2>> Evaporator 3 >> Evaporator 1 d) Evaporator 3 >> Evaporator 2 >> Evaporator 1 MCQ

MCQ:

20) Identify the following evaporator. a) Basket type short tube evaporator b) Standard type short tube evaporator c) Basket type long tube evaporator d) Standard type long tube evaporator MCQ

References:

C.V.S subrahmanyam et al., pharmaceutical engineering principles and practices - evaporation, 2001. G. K. Jani , Pharmaceutical Engineering-II, B .S . Shah Prakashan , Fifth Edition, 2008. Sanjay K Jain et al., Bentley’s Textbook of Pharmaceutics, Elsevier, 8 th edition, 2012. R. M. Mehta , Pharmaceutics-I ,1996. Anant Paradkar , Intorduction to Pharmaceuticle Engineering, Nirali Prakashan , 10 th edition, 2007. References

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