Separation Processes Flashcards
The distribution equilibrium for A between an extract solvent S and a
raffinate solvent B is given Y=2X where Y=mass of A per unit mass of S,
X=mass of A per unit mass of B. The extract and raffinate solvents are
immiscible with each other at all concentrations of A. From these data,
calculate the amount of extract solvent needed per 100 kg solution containing
30% A in B in 95% of A is to be removed for Single stage contact
A. 665 kg
C. 180 kg
B. 565 kg
D. 70 kg
665 kg
The distribution equilibrium for A between an extract solvent S and a
raffinate solvent B is given Y=2X where Y=mass of A per unit mass of S,
X=mass of A per unit mass of B. The extract and raffinate solvents are
immiscible with each other at all concentrations of A. From these data,
calculate the amount of extract solvent needed per 100 kg solution containing
30% A in B in 95% of A is to be removed for Three-stage batch contact, one third of the solvent will be used in
each contact
A. 60 kg
C. 210 kg
B. 665 kg
D. 180 kg
180 kg
Powdered limestone (CaCO3) containing 10000 ppm NaOH is to be washed in a
two-step continuous counter current washing system to remove most of the
NaOH. Two cells and 100000 L of water per 10 MT/day of limestone feed are
used. The slurry discharged and removed from the underflow contains 0.091 MT
of water per MT CaCO3. Assuming complete mixing and washing, calculate the
NaOH content of the washed and dried limestone in ppm.
A. 0.77 ppm
C. 0.82 ppm
B. 0.65 ppm
D. 0.97 ppm
0.82 ppm
Ten kg of a solid containing 45% of soluble material were treated with 15
kg of a solvent containing the same solute at 2% concentration in a vessel
under constant agitation. After a long time, the solution and the solid were
separated by pressing. The solid analyzed 0.8 kg of solvent per kg of inert
solid. The extract quantity obtained in kg was therefore
A. 14
C. 28
B. 22
D. 19
14
It is desired to produce an overhead product containing 80 mol% benzene
from a feed mixture of 68 mol% benzene and 32 mol% toluene. If the mixture
is subjected to equilibrium distillation at 1 atm, what is the fraction of
the liquid that is vaporized?
A. 1/3
C. 1/2
B. 1/4
D. 2/3
1/3
A vessel contains a liquid mixture of 50% benzene and 50% toluene by
weight at 1000C. Calculate the average molecular weight of the vapor in
contact with the solution.
A. 85 g/mol
C. 84 g/mol
B. 82 g/mol
D. 86 g/mol
82 g/mol
A 537 kg solution of 50% wt octane and 50% wt heptane is batch-distilled
until only 4.74 lbmols remain in the still. Assuming α=2.0, calculate the
total moles of distillate
A. 6.36 lbmol
C. 8.34 lbmol
B. 5.09 lbmol
D. 7.75 lbmol
. 6.36 lbmol
A 537 kg solution of 50% wt octane and 50% wt heptane is batch-distilled
until only 4.74 lbmols remain in the still. Assuming α=2.0, calculate the percentage by mol of heptane in the distillate
A. 40%
C. 30%
B. 50%
D. 60%
60%
A 537 kg solution of 50% wt octane and 50% wt heptane is batch-distilled
until only 4.74 lbmols remain in the still. Assuming α=2.0, calculate the octane concentration of the residue by weight
A. 40%
C. 30%
B. 50%
D. 60%
60%
The vapor pressures of n-heptane and toluene at 373 K are 106 and
73.7kN/m2 respectively. What is the mole fraction of n-heptane in the vapor
phase at 373 K if the total pressure is 101.3kN/m2?
A. 0.856
C. 0.894
B. 0.942
D. 0.969
0.894
It is desired to reduce the concentration of pyridine in 500 kg of
aqueous solution from 20 weight percent to 5 wt percent in a single batch
extraction using chlorobenzene as solvent. Equilibrium compositions (end
points of the tie line) in terms of weight percent of pyridine-waterchlorobenzene are (5, 95, 0) and (11, 0, 89). The amount of pure solvent
required in kg for the operation is
A. 607
C. 639
B. 931
D. 1501
639
One hundred kg of a solid containing 40% solute A and 60% inert B is treated
with solvent C in a single stage single contact extraction. The extracted
solids are then screw pressed. The pressed solids contain 1.2 kg solution
per kg of inert. Entrainment of solids in the extract may be neglected.
The mass fraction of the solute in the extract if 90% of the solute in
the feed is to be recovered in a single stage contact is
A. 0.03
C. 0.07
B. 0.06
D. 0.05
0.06
One hundred kg of a solid containing 40% solute A and 60% inert B is treated
with solvent C in a single stage single contact extraction. The extracted
solids are then screw pressed. The pressed solids contain 1.2 kg solution
per kg of inert. Entrainment of solids in the extract may be neglected.
The percent recovery of the solute if the extraction is carried out in
two crosscurrent stages if 50% of the solvent amount in problem no. 12 is
used in each stage is
A. 95%
C. 97%
B. 90%
D. 94%
97%
Cod liver oil is obtained from crushed livers by extraction with an organic
solvent. A sample that contains 0.335 kg of oil per each kg of exhausted
liver is fed into a multistage extractor that operates under countercurrent,
where pure organic solvent is employed. It is desired to recover 90% of the
oil in the final overflow, with a composition 60% in weight of oil. If
retention of the solution is 2 kg per each 3.2 kg of insoluble solids,
calculate the amount of solvent required and the number of ideal stages
required to carry out the desired extraction. Calculations are made assuming
that 100 kg of food is introduced into the extractor.
Amount of solvent required
A. 40 kg
C. 50 kg
B. 60 kg
D. 70 kg
60 kg
Cod liver oil is obtained from crushed livers by extraction with an organic
solvent. A sample that contains 0.335 kg of oil per each kg of exhausted
liver is fed into a multistage extractor that operates under countercurrent,
where pure organic solvent is employed. It is desired to recover 90% of the
oil in the final overflow, with a composition 60% in weight of oil. If
retention of the solution is 2 kg per each 3.2 kg of insoluble solids,
calculate the amount of solvent required and the number of ideal stages
required to carry out the desired extraction. Calculations are made assuming
that 100 kg of food is introduced into the extractor.
15. Number of ideal stages
A. 6
C. 5
B. 4
D. 3
6
A countercurrent extraction battery is used to extract NaOH from
theoretical feed of NaOH and CaCO3 produced by the causticization of lime,
but with 4 lb H2O per lb CaCO3. The final extract solution is to contain 10%
NaOH on recovery of 98% of the NaOH. How many theoretical stages will be
required? The underflow may be assumed constant at 2 lb solution per lb
CaCO3.
A. 2
C. 4
B. 3
D. 5
4
If the operation of the extraction units could be improved so that the
underflow contained only 1 lb solution per lb CaCO3, how many stages would
be required?
A. 2
C. 4
B. 3
D. 5
3
A multiple contact extraction is to treat 1.25 tons per hour of dry black
ash containing 40% Na2CO3 and 60% insoluble matter with 30 gpm of water. If
5% of the Na2CO3 remains unextracted, calculate the number of stages. The
mass ratio of insoluble matter to solvent in the underflow from the stage is
1:2.
A. 2
C. 3
B. 1
D. 4
2
Two ideal cross-current stages operate to extract P from a feed
containing P and Q. The mass flowrates of P and Q fed to stage 1 are 1000
kg/h and 10000 kg/h, respectively. Pure solvent (S) is injected at mass
flowrates of 5000 kg/h and 15000 kg/h to stages 1 and 2, respectively. The
equilibrium relation is given by Y* = 1.5X, where Y is the mass of P per
unit mass of S in the extract, which is in equilibrium with the raffinate.
The mass flowrate of P (in kg/hr) in the raffinate from stage 2 is _____
A. 188 kg/hr
C. 195 kg/hr
B. 176 kg/hr
D. 150 kg/hr
176 kg/hr
.Streptomycin is used as an antibiotic to fight bacterial diseases, and is
produced by the fermentation of a bacterium in a biological reactor with a
nutrient of glucose and amino acids. After the fermentation process,
Streptomycin is recovered by contacting the fermentation broth with an
organic solvent in an extraction process. The extraction process is able to
recover the Streptomycin because Streptomycin has a greater affinity for
dissolving in the organic solution than in the aqueous solution.
Determine the mass fraction of Streptomycin in the exit organic solvent
assuming that no water exits with the solvent exits with the aqueous
solution. Assume that the density of the aqueous solution is 1 g/ml and
the density of the organic solvent is 0.6 g/ml.
A. 0.25
C. 0.34
B. 0.19
D. 0.48
0.25
Which of the following operations does not involve leaching?
a. Dissolving gold from ores.
b. Dissolving pharmaceutical products from bark or roots.
c. Dissolving sugar from the cells of the beet.
d. Removing nicotine from its water solution by kerosene.
Removing nicotine from its water solution by kerosene.
Tea percolation employs
a. solvent extraction
c. absorption
b. leaching
d. adsorption
leaching
Neem oil is a traditional plant product which possesses
spermicidal properties. A group of students working on their
investigatory project wanted to test how effective the said oil was
as contraceptive by using it as a component for contraceptives.
The students were able to gather 5 kg of Neem Tree Seeds that
contains 30% of soluble oil and 70% inert solids and they decided
to use 5 kg of pure hexane to extract the oil. What percentage of
oil will they be able to recover given that the ratio of the liquid to
solid components in the underflow is 0.5? Assume ideal
leaching.
a. 88%
c. 73%
b. 93%
d. 65%
c. 73%
Which of the following is the most commonly used leaching
solvent in vegetable oil industry?
a. phenol
c. furfural
b. hexane
d. liquid SO2
hexane