IBX- Mass Transfer 4-6 Flashcards
Boiling point diagram is
not affected by pressure.
affected by pressure.
a plot of temperature vs. liquid composition.
a plot of temperature vs. vapour composition.
affected by pressure.
When acetone is added in a two layer mixture of methyl isobutyl ketone and water at 30°C, the acetone distributes between the two layers and the composition of the layer follows two solubility curves. For this system,
as the acetone concentration increases, the solubility curves approach each other.
both the phases become identical at a particular common point on both the solubility curves called the plait point.
the distribution curve which is a plot between x (acetone concentration in one phase) and y (acetone concentration in other phase) is analogous to x-y curve used in distillation and absorption terminates on the x = y diagonal at the concentration of the plait point.
all (a), (b) and (c).
all (a), (b) and (c).
Steam distillation is used to
reduce the number of plates.
avoid thermal decomposition of a component.
increase the efficiency of separation.
increase the total pressure of distillation.
avoid thermal decomposition of a component.
Freundlich equation applies to the
adsorption of solute from
dilute solutions, over a small concentration range.
gaseous solutions at high pressure.
concentrated solutions.
none of these.
dilute solutions, over a small concentration range.
For ethanol-water system, the lowering of distillate quality from 95% to 92% will cause __________ plate requirement.
no change in theoretical
marginal decrease in the number of
major decrease in the number of
none of these
marginal decrease in the number of
The apex of an equilateral-triangular coordinate (in ternary liquid system) represents a/an
pure component
binary mixture
ternary mixture
insoluble binary system
pure component
The diffusivity (D) in a binary gas mixture is related to the pressure (P) as
D∝P^0.5
D∝ 1/p^0.5
D∝1/p
D∝1/p^1.5
D∝1/p
A slurry is to be dried to produce flaky solid. Which dryer would you recommend ?
Spray dryer
Drum dryer
Rotary dryer
Dielectric dryer
Spray dryer
Which of the following psychrometric processes is followed by water vapour laden unsaturated air, when it is passed through solid or liquid adsorbent ?
Cooling and dehumidification.
Heating and dehumidification at almost constant wet bulb temperature.
Dehumidification with dry bulb temperature remaining constant.
None of these.
Heating and dehumidification at almost constant wet bulb temperature.
In gas-liquid contact operation, the number of ideal stages, N=(xA-xB)/(xb-x^b). This is true when the stripping factor ‘S’ is
S > 1
S < 1
S = 1
S = ∞
S > 1
The cooling effect in a cooling tower can not be increased by
increasing the air velocity over the wet surfaces.
reducing the humidity of entering air.
lowering the barometric pressure.
none of these.
none of these.
The value of NA/(NA + NB) for steady state molecular diffusion of gas ‘A’ through non-diffusing gas ‘B’ is
1
∞
0.5
2
1
The humid volume may be increased by increasing the
temperature at constant humidity.
humidity at constant temperature.
both (a) and (b).
neither (a) nor (b).
both (a) and (b).
Pick out the wrong statement
Co-current absorbers are usually used, when the gas to be dissolved in the liquid is a pure substance.
In case of gas absorption, HETP is equal to HTU, when both the operating line & the equilibrium lines are parallel.
Hatta number is important in case of gas absorption with chemical reaction.
In actual practice, absorption is an en-dothermic process, while stripping is an exothermic process.
In actual practice, absorption is an en-dothermic process, while stripping is an exothermic process.
When the mixture to be distilled has a very high boiling point and the product material is heat sensitive, the separation technique to be used is __________ distillation.
continuous
steam
azerotropic
none of these
steam
Large scale drying of wheat is done in a __________ dryer.
fluidised bed
spouted bed
tray
vacuum rotary
spouted bed
Azeotropic distillation is employed to separate
constant boiling mixture.
high boiling mixture.
mixture with very high relative volatility.
heat sensitive materials.
constant boiling mixture.
The drying time between fixed moisture content within diffusion controlled ‘falling rate period’ is proportional to (assuming that drying occurs from all surfaces of the solid) (where, T = thickness of the solid )
sqrt(T)
T
T^2
T^3
T^2
At the boiling point of the liquid at the prevailing pressure, the saturated absolute humidity becomes
1
0
∞
none of these
∞
Use of natural draft cooling tower is practised, when the air has low
humidity
temperature
both ‘a’ & ‘b’
neither ‘a’ nor ‘b’
both ‘a’ & ‘b’
Pressure drop through plate tower as compared to that through packed tower, for the same duty will be
less
more
equal
either (a) or (b); depends on the packing height
more
Dimension of mass diffusivity is the same as that of
kinematic viscosity
dynamic viscosity
surface tension
pressure
kinematic viscosity
Dorr thickener is an equipment used for
classification
sedimentation
clarification
leaching
sedimentation
Steam distillation is used to separate
azeotropes.
high boiling substances from nonvolatile impurities.
heat sensitive materials.
mixtures of low relative volatility.
high boiling substances from nonvolatile impurities.
In distillation where q is defined as the moles of liquid flow in the stripping section per mole of feed introduced, for saturated liquid feed
q > 1
q < 1
q = 1
q = 0
q = 1
Which of the following is an undesirable property in a tower packing ?
Large surface per unit volume.
Large free cross-section.
Low weight per unit volume.
Large weight of liquid retained.
Large weight of liquid retained.
Water entrained by circulating air in cooling towers is termed as
drift
blow down
vapor load
none of these.
drift
A 25 cm x 25 cm x 1 cm flat sheet weighing 1.2 kg initially was dried from both sides under constant drying rate conditions. It took 1500 seconds for the weight of the sheet to reduce to 1.05 kg. Another 1m x 1m x 1cm flat sheet of the same material is to be dried from one side only.Under the same constant drying rate conditions, the time required for drying (in seconds) from its initial weight of 19.2 kg to 17.6 kg is
1000
1500
2000
2500
1000
With increase in temperature, the rate of leaching increases, because the
diffusivity of solute increases.
viscosity of solvent decreases.
thermal conductivity of solute increases.
none of these.
diffusivity of solute increases.
Humidity chart is useful for the solution of problems concerning condensation, vaporisation and air conditioning. At a given dry bulb temperature, value of humidity obtained from the humidity chart directly, is in terms of __________ humidity.
molal
relative
percentage
none of these
molal
The Kundsen diffusivity is proportional to (where, T = absolute temperature)
sqrt(T)
T^2
T
T^4
sqrt(T)
In case of constant underflow extraction operation, the __________ at all solute concentration.
solids are drained to the same extent
ratio of the insoluble to solution is constant
both(a) & (b)
neither (a) nor (b)
both(a) & (b)
In an absorption coloumn, the flooding velocity for random packing is __________ that for stacked/regular packing.
greater than
smaller than
equal to
either (a), or (b) ; depends on the type of packing
smaller than
The relation among various mass transfer co-efficients (M.T.C) for ideal gases is given by (where, Kc & Km are M.T.C. for equimolar counter diffusion with concentration & mole fraction respectively as the driving force. and, Kp = M.T.C. for diffusion of a gas through a stagnant inert gas with pressure as driving force.)
Kc = Kp = Km
Kc = Kp/RT = Km . RT/P
Kc = Kp . RT = Km . RT/p
none of these
Kc = Kp . RT = Km . RT/p
With increase in temperature, the leaching rate increases because of the
increased diffusivity.
decreased viscosity of liquid.
both (a) and (b).
neither (a) nor (b).
both (a) and (b).
Leaching of uranium ore and gold ore is done in
centrifugal extractor
Pachuka tanks
Bollman extractor
none of these
Pachuka tanks
Blowdown in a cooling tower
means discarding a small fraction of circulating water to prevent and limit the concentration of salt and impurities.
increases the scale forming tendencies of water.
is undesirable.
all (a), (b) & (c).
means discarding a small fraction of circulating water to prevent and limit the concentration of salt and impurities.
During constant rate period, the rate of drying decreases with the
decrease in air temperature
increase in air humidity
both (a) and (b)
neither (a) nor (b)
both (a) and (b)
Antibiotics are best handled in a
Podbielniak extractor.
sieve tray contractor.
rotating disc contactor.
pulsed column extractor.
Podbielniak extractor.
The fixed cost of a distillation column at minimum reflux ratio is
minimum
infinite
optimum
none of these
infinite
__________ extractor uses centrifugal force for separating the two phases.
Treybal
Schiebel
Podbielniak
None of these
Podbielniak
In a binary distillation column, if the feed contains 40 mole % vapour, the q line will have a slope of
1.5
-0.6
-1.5
0.6
-1.5
Pick out the wrong statement.
Mechanical agitation is required, if the system has low interfacial tension.
Seive tray towers are generally used for systems having low interfacial tension.
When Henry’s law constant is very small, then the mass transfer rate is controlled by the gas film resistance.
Taylor-Prandtl analogy for heat and mass transfer considers the transfer through both laminar and turbulent layers.
Mechanical agitation is required, if the system has low interfacial tension.
Acetic acid will be most economically separated from a dilute solution of acetic acid in water by
solvent extraction
continuous distillation
evaporation
absorption
solvent extraction
Design calculation for multiple component distillation is done by
Ponchon-Savarit method
Mccabe-Thiele method
enthalpy concentration method
tray to tray calculations.
tray to tray calculations.
To get high tray efficiency
interfacial surface between liquid and gas phase should be large.
time of contact between the two phases should be less.
gas velocity should be very low.
liquid entrainment should be severe.
interfacial surface between liquid and gas phase should be large.
The mass transfer co-efficient for a solid sphere of radius ‘a’ dissolving in a large volume of quiescent liquid, in which D is the diffusivity of solute, is
D/a
D/2a
proportional to sqrt(D)
dependent on the Reynolds number
dependent on the Reynolds number
Pick out the wrong statement. Generally for physical adsorption, a gas of
higher molecular weight is adsorbed in preference to a gas of low molecular weight.
high critical temperature is adsorbed in preference to a gas of low critical temperature.
low volatility is adsorbed in preference to a gas of high volatility.
none of these.
none of these.
In most of the mechanically agitated liquid-liquid extractors, baffles or horizontal compartmental plates are provided, which helps in
reducing the axial mixing.
increasing the rate of extraction.
maintaining the concentration difference between the two phases.
all ‘a’, ‘b’ & ‘c’.
all ‘a’, ‘b’ & ‘c’.
In a vapor-liquid contacting equipment, the overall gas phase mass transfer co-efficient (M.T.C), KG is related to individual co-efficients (KG and KL) as
Kg=(1/Kg)+(m/Kl)
1/Kg=(1/Kg)+(m/Kl)
1/Kg=(1/Kl)=(m/Kg)
Kg=(1/Kl)+(m/Kg)
1/Kg=(1/Kg)+(m/Kl)
Solvent extraction is the terminology applied to the liquid-liquid extraction, which is preferred for the separation of the components of liquids, when
extracting solvent is cheaply & abundantly available.
one of the liquid components is heat sensitive.
viscosity of liquid components is very high.
one of the liquid components has very high affinity towards the solvent.
one of the liquid components has very high affinity towards the solvent
Inside the distillation column, the
driving force for the vapour flow is the pressure drop.
liquids are not always at their bubble points.
pressure increases gradually from bottom to the top of the column.
none of these
driving force for the vapour flow is the pressure drop.
Diffusivity in concentrated solutions differs from that in dilute solutions, because of the changes in
viscosity with concentration.
degree of ideality of the solution.
both (a) and (b).
neither (a) nor (b).
both (a) and (b).
Occurrence of ‘case hardening’ during drying of a high moisture solid cake __________ the drying rate.
increases
decreases
does not affect
exponentially increases
decreases
Which of the following is not a continuous drier ?
Drum drier
Spray drier
Tunnel drier
Tray drier
Tray drier
Humidification involves mass transfer between a pure liquid phase and a fixed gas, which is
insoluble in the liquid
soluble in the liquid
non-ideal in nature
at a fixed temperature
insoluble in the liquid
__________ is the temperature at which a gas-vapor mixture becomes saturated, when cooled at constant total pressure out of contact with a liquid.
Dew point
Bubble point
Dry bulb temperature
Wet bulb temperature
Dew point
Rate of leaching increases with increasing
temperature
viscosity of solvent
pressure
size of the solid
temperature
An azeotropic mixture is a __________ mixture.
binary
ternary
constant boiling point
none of these
constant boiling point
Pick out the wrong statement.
In the McCabe-Thiele diagram for binary distillation, vertical feed line represents saturated liquid feed and horizontal feed line represents saturated vapour feed.
In small columns, local efficiency is larger than Murphree efficiency; in large columns local efficiency is smaller than Murphree efficiency.
For Laminar flow over a plate of length L, the local mass transfer co-efficient at a distance L from the leading edge is 1.5 x 10-2m/s. Then the average mass transfer co-efficient for the plate is 2 x 10-2m/s.
The concentration and hydrodynamic boundary layers over a flat plate are of equal thickness, if Schmidt number is equal to unity.
For Laminar flow over a plate of length L, the local mass transfer co-efficient at a distance L from the leading edge is 1.5 x 10-2m/s. Then the average mass transfer co-efficient for the plate is 2 x 10-2m/s.
Molecular seives are regenerated by heating to __________ °C.
< 150
200-330
> 500
> 1000
200-330
In continuous distillation, the internal reflux ratio (Ri) and the external reflux ratio (Re) are related as
Ri=Re/1-Re
Ri=1-Re/Re
Ri=Re
Ri=Re/1+Re
Ri=Re/1+Re
In a counter-current extractor, as the axial mixing increases, the extraction efficiency
increases
decreases
remains unchanged
depends on the pressure of the system
decreases
Heat sensitive materials like certain pharmaceuticals and food stuffs can be dried in a/an __________ dryer.
indirect tray
spray
freeze
none of these
freeze
In extractive distillation, solvent is
added to alter the relative volatility of the mixture.
of high volatility.
present in overhead stream.
of high viscosity to give high tray efficiency.
added to alter the relative volatility of the mixture.
Radioactive nuclear waste is treated in
mixer-settler extractor
rotating-disc contactor
pulsed column extractor
Bollman extractor
pulsed column extractor
Large scale drying of sugar is done in a __________ dryer.
spouted bed
tray
rotary
truck
rotary
__________ temperature is the steady state temperature attained by a small amount of liquid evaporating into a large quantity of unsaturated gas-vapor mixture.
Dry bulb
Wet bulb
Dew point
none of these
Wet bulb
The drying time between fixed moisture contents within the ‘constant rate period’ is proportional to (assuming that drying occurs from all surfaces of the solid) (where, T = thickness of the solid )
sqrt(T)
T
T^1.5
T^3
T
_________ equation applies to diffusivities in liquids.
Gilliland
Hirschfelder
Wilke and Chang
none of these
Gilliland
A packed tower compared to a plate tower for a particular mass transfer operation
incurs smaller pressure drop.
allows installation of cooling coils.
is less costly when built in large sizes/diameters.
is more suitable, if suspended solids are present in fluid streams.
incurs smaller pressure drop.
Which of the following is the most commonly used leaching solvent in vegetable oil industry ?
Phenol
Hexane
Furfurol
Liquid SO2
Hexane
In an absorber, HETP does not vary with the
flow rate of liquid
flow rate of gas
type and size of packing
none of these
none of these
Large quantity of silica gel is normally dried in a __________ dryer.
freeze
through circulation
rotary vacuum
tray
through circulation
For the same system, if the same liquid used in an absorber is decreased, the tower height will
increase
decrease
remain unaffected
decrease or increase ; depends on the type of liquid
increase
Hydrogenation of oil is carried out in a/an __________ in Vanaspati manufacturing plant.
agitated vessel
sieve tray column
bubble cap column
packed tower
agitated vessel
Sides of equilateral-triangular co-ordinates (on which ternary liquid system is plotted) represent
a pure component.
a binary mixture.
a ternary mixture.
partially miscible ternary system.
a binary mixture.
In distillation column design, the McCabe-Thiele procedure is inadequate and a Ponchan-Savarit procedure is needed, when
saturated feed is not used.
an azeotrope forms.
the latent heat of vaporisation of the more and less volatile components are greatly different.
a total condenser is used.
a total condenser is used.
In an interphase mass transfer process, the lesser the solubility of a given solute in a liquid, the higher are the chances that the transfer process will be
liquid phase resistance-controlled.
gas phase resistance controlled.
impossible.
driven by a non-linear driving force.
gas phase resistance controlled.
As the reflux ratio decreases, the
separation becomes more efficient.
number of plates increases.
column diameter increases.
none of these.
number of plates increases.
Which of the following equipments is not used for gas dispersion ?
Agitated vessels
Bubble cap tray towers
Perforated sieve tray towers
Spray towers
Spray towers
One mole feed of a binary mixture of a given composition is flash vaporised at a fixed P and T. If Raoult’s law is obeyed, then changing the feed composition would effect
the product composition but not the fraction vaporised.
the product composition as well as the fraction vaporised.
the fraction vaporised but not the product composition.
neither the product composition nor the fraction vaporised.
the fraction vaporised but not the product composition.
The equation, NA=(Dab(Pt))/RTz (y1-y2) is for
steady state equimolar counter diffusion
Fick’s first law of diffusion
steady state diffusion for stagnant case
liquid M.T.C. by penetration theory.
steady state equimolar counter diffusion
With increase in the liquid flow rate at a fixed gas velocity in a randomly packed counter current gas-liquid absorption column, the gas pressure drop
decreases
remains unchanged
increases
decreases exponentially
increases
NA=(Dab(Pt))/(RTz . Pbm) (y1-y2)
Fick’s second law of diffusion.
stready state diffusion for stagnant case.
liquid M.T.C. by Higbie penetration theory.
none of these.
stready state diffusion for stagnant case.
Which of these columns incurs the lowest pressure drop ?
Packed column (with stacked packing)
Packed column (with dumped packing)
Bubble plate column
Pulse column
Packed column (with stacked packing)
In the desorption of highly soluble gas from the liquid, the main resistance will be in the __________ phase.
gas
liquid
both (a) & (b)
neither (a) nor (b)
liquid
If G = insoluble gas in gas stream and L = non-volatile solvent in liquid stream, then the slope of the operating line for the absorber is
L/G
G/L
always < 1
none of these
L/G
Which of the following remains constant during evaporative cooling process with recirculated water supply ?
Relative humidity
Partial pressure of vapour
Wet bulb temperature
None of these
Wet bulb temperature
For stripping of a gas in a counter current stripper, the operating line
lies above the equilibrium curve.
lies below the equilibrium curve.
can lie above or below the equilibrium curve.
is always parallel to the equilibrium curve.
can lie above or below the equilibrium curve.
Which of the following same diameter columns gives lowest pressure drop per unit height ?
Bubble-cap column
Sieve-plate column
Packed column (stacked)
Randomly packed column
Packed column (stacked)
Diffusion in concentrated solutins differs from that in dilute solutions, because of the change in the __________ with the concentration of the solution.
degree of ideality
viscosity
both ‘a ‘& ‘b’
neither ‘a’ nor ‘b’
both ‘a ‘& ‘b’
Stage efficiency in a leaching process depends on the
time of contact between the solid and the solution
rate of diffusion of the solute through the solid and into the liquid
both (a) and (b)
vapour pressure of the solution
both (a) and (b)
Operating velocity in a packed tower is usually __________ the flooding velocity.
half
twice
equal to
more than
half
The Knudsen diffusivity is dependent on the
molecular velocity only.
pore radius of the catalyst only.
molecular mean free path only.
molecular velocity and por radius of the catalyst.
molecular velocity and por radius of the catalyst.
Minimum possible diameter of a packed coloumn is decided mainly by the
flooding
gas viscosity
liquid density
liquid hold up
flooding
Solvent used in extractive distillation
is of low volatility.
forms a low boiling azeotrope.
forms a high boiling azeotrope.
does not alter the relative volatility of the original components.
forms a low boiling azeotrope.
Capacity of a rotary dryer depends on its
r.p.m
inclination with ground surface
both (a) and (b)
neither (a) nor (b)
both (a) and (b)
The cooling effect in a cooling tower can be speeded up by
increasing the air velocity and area of exposed wet surface.
reducing the barometric pressure.
reducing the humidity of the air.
all (a), (b) and (c).
all (a), (b) and (c).
basta maangas
1
When both the fluids flow concurrently in an absorber, the slope of the operating line is
- ve
+ ve
1
-1
- ve
The percentage humidity is less than the relative humidity only at __________ percent humidity.
zero
hundred
both zero and hundred
none of these
both zero and hundred
Back-trapping in a distillation column
increases tray efficiency.
decreases tray efficiency.
reduces pressure drop.
is desirable, as it provides improved vapour-liquid contact.
decreases tray efficiency.
Flooding in a vapor-liquid contacting equipment occurs in a tray, when the pressure drop through a tray is __________ the liquid head available in the downcomer.
less than
more than
same as
very much less
more than
Milk is dried usually in a __________ dryer.
freeze
spray
tray
rotary
spray
At a given equilibrium pressure, with increase in temperature, the concentration of adsorbed gas on solid adsorbant
increases
decreases
remains unchanged
increases exponentially
decreases
Which of the following adsorbent is used to decolourise yellow glycerine ?
Silica gel
Alumina
Fuller’s earth
Activated carbon
Activated carbon
GRAPH NANAMAN TANGINA
BRRR
In a distillation column, with increase in the reflux ratio, the heat removed in the cooler
increases.
decreases.
remains unaffected.
and the heat required in reboiler decreases.
increases.
Pick out the wrong statement.
Constant pressure distillation can not separate an azeotropic mixture.
Relative volatility of a binary mixture changes appreciably with the minor change in temperature.
The relative volatility of a binary mixture at azeotropic composition is unity.
Flash distillation is practised on wide spread scale in petroleum refinery.
Relative volatility of a binary mixture changes appreciably with the minor change in temperature.
Which of the following is not a unit of mass transfer co-efficient ?
Moles Transferred/(time)(area)(mole fraction)
Moles transferred/(time)(area)(pressure)
Moles transferred/(time)(area)(massA/MassB)
None of these
None of these
The falling rate period in the drying of a solid is characterised by
increase in rate of drying.
increasing temperatures both on the surface and within the solid.
decreasing temperatures.
none of these.
increasing temperatures both on the surface and within the solid.
In which of the following unit operations, the selectivity is an important parameter ?
Distillation
Solvent extraction
Absorption
None of these
Solvent extraction
Which of the following is an undesirable characteristic for the solvent used in gas absorption ?
Low vapor pressure
Low viscosity
High gas solubility
None of these
None of these
Which of the following equipments is not used for liquid dispersion ?
Wetted wall towers
Packed towers
Venturi scrubbers
Agitated vessels
Agitated vessels
Diameter of raschig rings used in packed tower in industry is normally around __________ inches.
2
8
12
18
2
The diffusion co-efficient in m2 /s. of acetic acid in benzene (liquid in liquid) is
2.09 x 10-4
2.09 x 10-5
2.09 x 10-9
2.09 x 10-12
2.09 x 10-9
Pick out the wrong statement.
The Reynolds analogy for mass transfer is given by Lewis relation and is applicable, when Schmidt number is one.
Sherwood number for flow in pipes can be expressed as the ratio of the concentration gradient at wall to the overall concentration difference.
According to film theory for equimolar counter diffusion, the mass transfer coefficient is given by sqrt(DAB)(b)P - 3, Q - 2
The z-component of the total mass flux of a component A in binary mixture of A and B is given by - Dab’.dCA/dz.
According to film theory for equimolar counter diffusion, the mass transfer coefficient is given by sqrt(DAB)(b)P - 3, Q - 2
In case of non-ideal gases and liquids, the molal diffusivity
varies inversely as the pressure.
varies directly as the pressure.
is independent of pressure.
is equal to the volumetric diffusivity.
is independent of pressure.
Condensation of a vapour-gas mixture just begins, when (where, p = partial pressure of the vapour P = vapour pressure of the liquid )
p = P
p»_space;P
p < P
p «_space;P
p = P
__________ number indicates the ratio of the rates of the heat and mass transfer incase of a cooling tower.
Sherwood
Stanton
Lewis
Peclet
Lewis
The expression, y(1 - x)/x(1 - y) is for
absorption factor
relative volatility
selectivity
Murphree efficiency
relative volatility
In physical terms, Schmidt number means
thermal diffusivity/mass diffusivity.
thermal diffusivity/momentum diffusivity.
momentum diffusivity/mass diffusivity.
mass diffusivity/thermal diffusivity.
momentum diffusivity/mass diffusivity.
In case of liquids, the binary diffusivity is proportional to (where, T = temperature)
T
sqrtT
T^2
1/T
T
The diffusivity, DAB (for component A diffusing in B) is equal to the diffusivity DBA (for component B diffusing in A) for a binary mixture of
Newtonion liquids
non-Newtonion liquids
ideal gases
real gases
ideal gases
Mass transfer co-efficient is directly proportional to DAB0.5, according to __________ theory.
penetration
surface renewal
film
none of these
penetration
Sand is dried in foundaries in a___drier.
rotary
fluidisedbed
vacuum
spray
fluidisedbed
Which of the following employs an accessory known as ‘drift eliminator’ ?
Multiple effect evaporator.
Mechanical draft cooling tower.
Rotary dryer.
Rotating disc contactor.
Mechanical draft cooling tower.
Pick out the correct statement.
Higher hold up of the solid in the rotary dryer results in better exposure of the solids to the gas.
The ‘Hatta number’ is important in problems involving gas absorption without chemical reaction.
For a non-reacting binary mixture of ideal gases, the partial pressure distribution of both components is linear in the case of steady state equimolal counter-diffusion.
Total reflux in case of distillation operation requires infinite number of plates for a binary system separation.
For a non-reacting binary mixture of ideal gases, the partial pressure distribution of both components is linear in the case of steady state equimolal counter-diffusion.
Pick out the correct statement.
For identical gas flow rates, less pressure drop occurs through a plate tower than through a packed tower.
Plate column can handle greater liquid loads without flooding than packed column, but the liquid hold up is more in the case of plate column.
For the same duty, plate columns weigh less than packed columns.
all (a), (b) and (c).
all (a), (b) and (c).
Humid volume is the total volume in m3 of 1 kg of
vapour laden gas at 1 atm. and room temperature.
gas plus its accompanying vapour at 1 atm. and room temperature.
gas plus its accompanying vapour at 1 atm. and gas temperature.
vapour laden gas at 1 atm. and gas temperature.
gas plus its accompanying vapour at 1 atm. and gas temperature.
Diameter to height ratio for a rashig ring is
1
0.5
2
8
1
The equipment used in the extraction of highly corrosive radio active liquids is
pulse column
spray column
mixer settler
baffle tower
pulse column
Advantage of continuous drying over batch drying is that the
drying cost per unit weight of dried product is less.
product with more uniform moisture content is produced.
equipment size required is smaller.
all ‘a’, ‘b’ & ‘c’
all ‘a’, ‘b’ & ‘c’
With increase in temperature, the rate of extraction in leaching (solid-liquid extraction system)
increases
decreases
remains unaffected
increases Linearly
increases
In a packed bed absorption column, the channelling will be noted by the
increase in flow rate.
sharp drop in pressure drop.
sharp rise in pressure drop.
none of these.
sharp drop in pressure drop.
Gaseous diffusivity at atmospheric pressure is of the order of __________ cm2/second.
1
1 to 5
5 to 10
> 10
1
In liquid-liquid extraction, the number of phases at plait point is
1
2
3
4
1
In a liquid-liquid extraction, 10 kg of a solution containing 2 kg of solute C and 8 kg of solvent A is brought into contact with 10 kg of solvent B. Solvent A and B are completely immiscible in each other whereas solute C is soluble in both the solvents. The extraction process attains equilibrium. The equilibrium relationship between the two phases is Y* = 0.9X, where Y* is the kg of C/kg of B and X is kg of C/kg of A. Choose the correct answer.
The entire amount of C is transferred to solvent B.
Less than 2 kg but more than 1 kg of C is transferred to solvent B.
Less than 1 kg of C is transferred to B.
No amount of C is tranferred to B.
The entire amount of C is transferred to solvent B.
he surface renewal frequency in Danckwerts’ model of mass transfer is given by (KL: mass transfer co-efficient)
sqrt(KL2.DA)
(KL)^2.DA
(KL)^2/DA
KL/DA^2
sqrt(KL2.DA)
If Rm is the minimum reflux ratio, the optimum reflux ratio may be around __________ Rm.
1.2 to 1.5
2.5 to 3
3 to 4
5
1.2 to 1.5
During dehumidification of unsaturated air wet bulb temperature & partial pressure of vapor are not constant. However, during evaporative cooling process with recirculated water supply, the __________ remains constant.
wet bulb temperature
partial pressure of water vapor
relative humidity
none of these
wet bulb temperature
In case of absorption, both the operating and equilibrium lines will be straight for
isothermal operation.
dilute solutions.
dilute solutions and isothermal operation.
none of these.
dilute solutions and isothermal operation.
Mass transfer co-efficient varies as DAB0.5, according to the __________ theory.
film
surface renewal
penetration
none of these
surface renewal
For an absorber, both equilibrium and operating line will be straight for
concentrated solution and non-isothermal operation.
dilute solution and non-isothermal operation.
dilute solution and isothermal operation.
concentrated solution and isothermal operation.
dilute solution and isothermal operation.
FIGURE
BWISET
Unsaturated air (with dry bulb and wet bulb temperatures being 45°C and 25°C respectively) is passed through a water spray chamber maintained at 23°C. The air will be cooled and
humidified with wet bulb temperature decreasing.
humidified at constant wet bulb temperature.
dehumidified.
none of these
humidified with wet bulb temperature decreasing.
Humid volume, at a given temperature is a/an __________ function of humidity.
inverse
exponential
linear
logarithmic
linear
The Schmidt number which is defined as, μ/ρ D, is the ratio of the
momentum diffusivity to the mass dif-fusivity.
thermal diffusivity to the mass diffusivity.
momentum diffusivity to the thermal diffusivity.
none of these.
momentum diffusivity to the mass dif-fusivity.
If f is defined as above, then which of the following applies to a feed at dew point ?
f = 1
f < 1
f > 1
0 < f < 1
f = 1
