SEPPROC Flashcards
Which of the following solutions will follow Raoult’s law most closely?
A solution of benzene, toluene and oxylene.
Boiling point diagram is
affected by pressure
The ease of difficulty of separating components by distillation is determined by the
relative volatility
Strictly speaking, the relative volatility of most ideal binary solution is
greatly affected by temperature
When the relative volatility of two miscible components is close to 1.00, the components can be separated by
extractive distillation
The physical separation of components in a miscible mixture by simultaneous evaporation and condensation is
distillation
In a batch distillation, the boiling point of the distillate product compared to the residue is
lower
Increasing the operating pressure of a distilling column
makes separation difficult
One mole feed of a binary mixture of a given composition is flash vaporized at a fixed P and T. If Raoult’s law is obeyed, then changing the feed composition would effect
the fraction vaporized but not the product composition
Steam distillation is used to
avoid thermal decomposition of a component.
The amount of steam required per unit quantity of distillate in case of steam distillation will be reduced by
raising the temperature and lowering the total pressure
In distillation, the cooled liquid stream returned to the column to a cool plate or stage is called
reflux
In a distilling column, the highest pressure will be at
the bottom
A heat transfer equipment to convert vapor to liquid is a/an
condenser
A reboiler provides heat to the
the bottom of a distilling column
The temperature in distilling column, from bottom to top
decreases
The theoretical minimum reflux ratio in distillation column is attained if the column has
infinite number of plates
If x co-ordinate of intersection point of feed line and rectifying sections operating line on equilibrium curve is same as the mole fraction of more volatile components in the feed, then the quality of feed is
saturated liquid
As the reflux ratio decreases, the
number of plates increases
In a distillation column, with increase in the reflux ratio, the heat removed in the cooler
increases
Fenske’s equation for determining the minimum number of theoretical stages in distillation column holds good, when the
relative volatility is reasonably constant
Inside the distillation column, the
driving force for the vapor flow is the pressure drop
On moving the feed line (q-line) from saturated liquid feed (vertical position) to saturated vapor feed (horizontal feed), if the slope of both the operating lines are to be increased, then it will result in
increased reflux ratio
In case of binary distillation, increasing the reflux ratio above optimum does not result in the increase of
area between operating line and 45° diagonal x-y diagram
Overall efficiency of the distillation column is
the ratio of number of ideal plates to actual plates
Pick out the correct statement.
a. Ponchon-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.
b. A sharp decrease in pressure drop is an indication of flooding in a distillation column.
c. Solvent used in extractive distillation should be of high volatility.
d. Flash distillation is suitable for separating components which have very close boiling temperature.
Ponchon-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.
Pick out the correct statement.
a. The slope of the stripping line is always less than unity.
b. For a given separation in a binary distillation column, with increase in reflux ratio (above the minimum reflux ratio), the fixed cost of the distillation column first increases and then decreases. c. In Ponchon-Savarit method of no. of theoretical plate determination, the stripping and rectifying operating lines are vertical at total reflux.
d. Kremsor-Brown-Souder’s equation is used to calculate the efficiency of a plate tower.
In Ponchon-Savarit method of no. of theoretical plate determination, the stripping and rectifying operating lines are vertical at total reflux.
Design calculation for multiple component distillation is done by
tray to tray calculations
Pick out the wrong statement:
a. Reboiler is not used in open steam distillation.
b. The separation of solutes of different molecular sizes in a liquid solution by use of a suitable membrane is called dialysis.
c. Freeze drying is used for the drying of fish.
d. Fenske-Underwood equation is used for calculating theoretical number of plates in a distillation column at normal operating reflux condition.
Fenske-Underwood equation is used for calculating theoretical number of plates in a distillation column at normal operating reflux condition
In extractive distillation, solvent is
added to alter the relative volatility of the mixture
Solvent used in extractive distillation
forms a low boiling azeotrope
Pick out the wrong statement.
a. Critical moisture content is not a property of the material itself. b. A sharp increase in pressure drop gives an indication of the flooding in a distillation column.
c. Separation of components is not possible in liquid extraction, if selectivity is unity.
d. Dehydration of ethyl alcohol is most economically done by molecular distillation at very high vacuum.
Dehydration of ethyl alcohol is most economically done by molecular distillation at very high vacuum
Azeotropic distillation is employed to separate
constant boiling mixture
The equilibrium liquid composition compared to the vapor composition in case of azeotropic mixture is
same
The equilibrium liquid composition compared to the vapor composition in case of azeotropic mixture is
same
Pick out the wrong statement.
a. The mole fraction of solute is directly proportional to the molality of a ‘dilute’ solution.
b. For a non-reacting binary mixture of ideal gases, the partial pressure distribution of both components is nonlinear in the case of steady state unimolal unidirectional diffusion.
c. Azeotropes obey Raoult’s law at all temperature.
d. The relative volatility of a binary mixture at the azeotropic composition is 1.
Azeotropes obey Raoult’s law at all temperature.
Pick out the system with minimum boiling azeotrope at 1 atm.
ethyl alcohol-water
Which of the following binary systems is an example of a maximum boiling azeotrope?
water-hydrochloric acid
A unit operation in which a soluble component is removed from an inert solid by a solvent which preferentially dissolves the soluble matter is known as
leaching
A unit operation in which a soluble component is removed from an inert solid by a solvent which preferentially dissolves the soluble matter is known as
leaching
The unit operation by which soluble components of a liquid mixture are dissolved in a liquid immiscible with the insoluble component is
solvent extraction
Tea percolation employs
leaching
Which of the following is the most commonly used leaching solvent in vegetable oil industry?
hexane
Leaching of sugar from sugar beets is done using
hot water
In a counter-current extractor, as the axial mixing increases, the extraction efficiency
decreases
Bollman extractor
is used for extraction of oil from oilseed
Acetic acid will be most economically separated from a dilute solution of acetic acid in water by
solvent extraction
Liquid-liquid extraction is based on the differences in
solubility
Radioactive nuclear waste is treated in
pulsed column extractor
The solvent used in liquid extraction should not have high latent heat of vaporization, because
the pressure drop and hence the pumping cost will be very high.
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.
In a counter-current liquid extractor
only one of the liquids may be pumped at any desired rate.
A coalescer in a mixer-settler liquid-liquid extraction column
all of these
Antibiotics are best handled in a
pulsed column extractor
Rose oil is extracted from rose leaves using distillation
steam distillation
When the solvent dissolves very little of solute then
large quantity of solvent is required to extract the solute
An ideal single stage extraction process is used to treat 100 mol/s of an organic feed solution. The solute concentration in this solution is to be reduced from 0.5 mol% to 0.1 mol%. A pure solvent S is used. To reduce the solvent requirement by half for the same separation
use another pure solvent S* whose partition coefficient is twice that of S
The triangle whose one corner coincides with the enriching line and the outer corner is on the stripping line is called the
feed plate
Flash distillation is suitable for the separation of components
having very wide boiling points.
Relative volatility varies with the concentration of component for an ideal solution. The relative volatity of a binary mixture may be defined as the ratio of vapor pressure of component ‘A’ to that of component ‘B’, when
vapor phase obeys Dalton’s law and liquid phase obeys Raoult’s law.
Leaching of coarse solid lumps is also termed as
percolation
In an operating distillation column, the
driving force for the vapor flow is the pressure drop, as the pressure decreases gradually from the bottom to the top of the column.
Large scale usage of flash distillation is practiced in
petroleum refinning
In case of steam distillation, the steam leaving the liquid is not completely saturated with distillate vapor, because
mixing of steam with the material being vaporised is not so intimate as to result in equilibrium condition.
For a binary mixture distillation process, the degree of freedom is 2. However, if the pressure is fixed in this process, the number of independent variables in this process will be
1
Which of the following is the most suitable for extraction in a system having very low density difference ?
Centrifugal extractor
Total reflux in a distillation operation requires minimum
number of plates
In batch distillation with constant reflux, overhead product composition __ with time.
decreases
Raoult’s law applies to the
solvents
In distillation, overhead product contains
any number of components
For the same feed, feed quality and separation (in a distillation column), with the increase of total pressure, the number of ideal plates will
increase
The operation involved when the soluble material is largely on the surface of an insoluble solid and is merely washed off by the solvent is called
elutriation or elution
Pick out the wrong statement.
a. Heat removal load on cooler remains constant, even with increase of the reflux ratio in a distillation column.
b. Different solids have different equilibrium moisture curves.
c. Total condenser or reboiler is considered equivalent to one theoretical plate in McCabe-Thiele method of theoretical plate calculation for distillation column.
d. Even a forced draft cooling tower can not cool water below the wet bulb temperature.
Heat removal load on cooler remains constant, even with increase of the reflux ratio in a distillation column.
An aqueous solution of methanol is to be distilled in a tray column. High pressure steam is available as a source of heat. For a given reflux ratio and overhead composition, two options are being explored; (i) a reboiler is used and (ii) no reboiler is used but steam is fed directly to the bottom of the column. As compared to option (i), in option (ii)
less number of trays are required.
Ponchan-Savarit method analyses the fractional equipment based on
both enthalpy and material balances.
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.
steam
The fixed cost of a distillation column at minimum reflux ratio is
infinite
__ extractor uses centrifugal force for separating the two phases.
Podbielniak
In most of the mechanically agitated liquid-liquid extractors, baffles or horizontal compartmental plates are provided, which helps in
All of these (maintaining the concentration difference between the two phases, increasing the rate of extraction, reducing the axial mixing)
Which of the following applies to a feed at dew point?
f = 1
Pick out the wrong statement.
a. With increase in pressure, the solubility of gases in solvent increases at a fixed temperature.
b. The capacity of a distillation column is maximum at total reflux.
c. In solvent extraction, the distribution coefficient should be as large as possible for solvent economy.
d. Decrease in Murphree plate efficiency is an indication of entrainment in distillation column.
The capacity of a distillation column is maximum at total reflux.
The relative volatility of a binary mixture at the azeotropic composition is
1
Which of the following is not a continuous leaching equipment?
Pachuka tank
High pressure at the bottom of a distillation tower handling heat sensitive materials results in
thermal decomposition of bottoms.
For a binary mixture with low relative volatility, continuous rectification to get pure products will require
high reflux ratio
In steam distillation, the
product must be immiscible with water.
