Mass Transfer

Packed

The ratio of number of ideal plates to actual plates.

both (b) and (c)

Heat transfer

reduce drying temperature.

higher relative humidity

absorption

both 'a' & 'b'

number of plates is infinity.

partial pressure of the vapour to the vapour pressure of the liquid at gas temperature.

decreases

electrical resistance

specific heat

increase 'S' and decrease 'G'.

1

decreases with decrease in pressure.

both (a) and (b)

Lewis number

line always lies above the equilibrium curve.

total cost first decreases and then increases.

0

Both (a) and (b)

both (b) and (c)

all (a), (b) and (c)

Flow rate of entering liquid

affected more by temperature than that for gases.

Multicomponent distillation.

Wetted wall column

spray chamber

an irreversible phenomenon.

all 'a', 'b' & 'c'.

solvents.

allowable gas and liquid velocities.

any number of components

decreases.

all (a), (b) and (c).

linear crystal growth rate does not depend on the crystal size.

is used for extraction of oil from oilseed.

heat and mass

all 'a', 'b', & 'c'.

increase

Ponchan-Savarit method is more accurate than McCabe-Thiele method to determine the number of theoretical stages required for the separation of non-ideal binary system by distillation.

vapour pressure of component A to that of component B.

elutriation or elution

surface evaporation of unbound moisture occurs.

71 min

all (a), (b) and (c).

Thermal

concentration

Heat removal load on cooler remains constant, even with increase of the reflux ratio in a distillation column.

Rotary dryer is suitable for drying sticky material.

low pressure drop and low hold up.

> 100

50%

ideal solutions

results due to very low gas velocity.

area between operating line and 45° diagonal x-y diagram.

mass transfer co-efficient.

the overhead product is minimum.

increases

packing may be crushed due to thermal expansion/contraction of the components of the equipments.

same

wetted wall

ethyl alcohol-water

rotary

linearly

Sherwood

0.215

its recovery cost by distillation may be prohibitatively high.

is greater than

litre

1

less number of trays are required.

exponential

Water-hydrochloric acid.

Peclet

In Ponchon-Savarit method of no. of theoretical plate determination, the stripping and rectifying operating lines are vertical at total reflux.

Electrodylsis is used in the manufacture of NaOH.

The driving force for mass transfer in a wet solid is its free moisture content.

avoid channelling

free

decreases

steam jet ejector with a barometric condenser

increased reflux ratio

Plate

ion-exchange

all (a), (b)&(c)

Azeotropes obey Raoult's law at all temperature.

acetone-carbon disulphide

A solution of benzene, toluene and oxylene.

decreases pressure drop, increases surface area.

both (a) and (b).

both parallel and straight

that of normal condensation.

carbon dioxide from gaseous stream using alkaline solution.

> 1

Fenske-Underwood equation is used for calculating theoretical number of plates in a distillation column at normal operating reflux condition.

heated cylinder

Dehydration of ethyl alcohol is most economically done by molecular distillation at very high vacuum.

large latent heat

raschig

infinity

hot water

both operating and equilibrium lines are parallel.

lift and shower the solids thus exposing it thoroughly to the drying action of the gas.

on heating, a vapor phase will appear ; while on cooling, a solid phase will appear.

none of these.

0.4

both 'a' & 'b'

1

absorption factor

both enthalpy and material balances.

always smaller than

operating line always lies below the equilibrium curve.

Infinity

is maximum

10-60

liquid side mass transfer co-efficient should be increased.

both (b) and (c)

integral heat of adsorption.

total reflux

all (a), (b) & (c)

only one of the liquids may be pumped at any desired rate.

None of these

individual mass transfer co-efficient (M.T.C.) in gaseous system.

less

greater than that computed for ideality.

increases

both (a) and (c)

7

affected by pressure.

all (a), (b) and (c).

avoid thermal decomposition of a component.

dilute solutions, over a small concentration range.

marginal decrease in the number of

pure component

Spray dryer

Heating and dehumidification at almost constant wet bulb temperature.

S > 1

none of these.

1

both (a) and (b).

In actual practice, absorption is an en-dothermic process, while stripping is an exothermic process.

steam

spouted bed

constant boiling mixture.

∞

both 'a' & 'b'

more

kinematic viscosity

v

high boiling substances from nonvolatile impurities.

q = 1

drift

1000

diffusivity of solute increases.

molal

both(a) & (b)

smaller than

both (a) and (b).

Pachuka tanks

means discarding a small fraction of circulating water to prevent and limit the concentration of salt and impurities.

both (a) and (b)

Podbielniak extractor.

infinite

Podbielniak

-1.5

Mechanical agitation is required, if the system has low interfacial tension.

solvent extraction

tray to tray calculations.

interfacial surface between liquid and gas phase should be large.

dependent on the Reynolds number

none of these.

all 'a', 'b' & 'c'.

one of the liquid components has very high affinity towards the solvent.

driving force for the vapour flow is the pressure drop.

both (a) and (b).

decreases

Tray drier

insoluble in the liquid

Dew point

temperature

constant boiling point

200-330

decreases

freeze

added to alter the relative volatility of the mixture.

pulsed column extractor

rotary

Wet bulb

T

Gilliland

incurs smaller pressure drop.

Hexane

none of these

through circulation

increase

agitated vessel

a binary mixture.

a total condenser is used.

gas phase resistance controlled.

number of plates increases.

Spray towers

the fraction vaporised but not the product composition.

steady state equimolar counter diffusion

increases

stready state diffusion for stagnant case.

Packed column (with stacked packing)

liquid

L/G

Wet bulb temperature

can lie above or below the equilibrium curve.

Packed column (stacked)

both 'a '& 'b'

both (a) and (b)

half

molecular velocity and por radius of the catalyst.

flooding

forms a low boiling azeotrope.

both (a) and (b)

all (a), (b) and (c).

T1-Dry bulb temp; T2-Wet bulb temp; T3-Dew point temp.

- ve

both zero and hundred

decreases tray efficiency.

more than

spray

decreases

Activated carbon

increases.

Relative volatility of a binary mixture changes appreciably with the minor change in temperature.

increasing temperatures both on the surface and within the solid.

Solvent extraction

None of these

Agitated vessels

2

is independent of pressure.

p = P

Lewis

relative volatility

T

momentum diffusivity/mass diffusivity.

ideal gases

penetration

fluidisedbed

Mechanical draft cooling tower.

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.

all (a), (b) and (c)

gas plus its accompanying vapour at 1 atm. and gas temperature.

1

pulse column

all 'a', 'b' & 'c'

increases

sharp drop in pressure drop.

1

The entire amount of C is transferred to solvent B.

1.2 to 1.5

wet bulb temperature

dilute solutions and isothermal operation.

surface renewal

dilute solution and isothermal operation.

0.6

humidified with wet bulb temperature decreasing.

linear

momentum diffusivity to the mass dif-fusivity.

f = 1

repeated coalescence & redispersion of the drop phase.

interface

Reynolds number in mass transfer is analogous to Grashoff number in heat transfer.

-ve

gas side

0.5

continuous

12

all (a), (b) and (c).

increases

The capacity of a distillation coloumn is maximum at total reflux.

1

Vapor phase obeys Dalton's law and liquid phase obeys Raoult's law.

less than

Sc / Pr

Pachuka tank

Pulsed column

equilibrium

unbound

isotopes of uranium

is computed from the slope of the upper operating line that is tangent to the equilibrium curve.

500

lower than

mass transfer co-efficient

In case of a stripper, the equilibrium curve is always below the operating line.

no separation will occur.

cylinder

Both (b) and (c)

Effectiveness of a mechanical draft cooling tower is reduced with increase in air wet-bulb temperature.

percolation

avoid channeling.

a pure substance

95

wetted wall

decreases.

Co-efficient = Flux/concentration difference.

the relative humidity decreases.

both (b) and (c)

0

equal to the heat of wetting.

1.25 to 2.0

The equilibrium moisture content of the solid can be reduced by increasing the absolute humidity.

petroleum refinning

thermal decomposition of bottoms.

azeotropic

relative volatility

Both (b) and (c)

tray

Butyl acetate

sticky

none of these.

partial pressure

temperature

both (b) and (c)

gas

Temperature of the solid

none of these

rotary

always lower than

bound

high reflux ratio

both (a) & (b)

both (a) & (b).

both (a) and (b)

spray dryer