SEPAPRO Flashcards
(10 cards)
During Ground roasted coffee contains 8% soluble solids, 2%
water, and 90% inert insoluble solids. In order to obtain an extract
with high soluble solids content without having to concentrate it
for spray drying, a countercurrent extraction process is to be used
to prepare the extract. It is desired that the final extract contains
0.15 kg soluble/ kg water and that the soluble of the spent coffee
grounds not to exceed 0.008 kg/kg dry inert solids. The coffee
grounds carry 1 kg water/ kg of soluble free inert solids and this
quantity is constant with the solute concentration in the extract.
Determine the number of extraction stages needed for this
process.
a. 3 c. 5
b. 4 d. 6
d. 6
In a salt recovery plant, rock salt is being leached to produce
industrial salt in a continuous counter current system consisting
of two ideal stages using water as leaching medium. the average
composition of the rock salt is: inerts = 70%, soluble salts = 25%,
moisture = 5%, all percentage by weight. The underflow from
each stage contains 0.3 kg of solution per kg of inerts. The plant
leaches 50 MT of rock salt per day using 50 MT of water.
- The quantity of soluble salts recovered in MT/day is
a. 12.1 c. 13.1
b. 14 d. 11.2 - The composition of salt in weight percent in the final underflow is
a. 0.88% c. 0.98%
b. 0.78% d. 0.68%
a. 12.1
a. 0.88%
A liquid mixture of acetaldehyde and toluene contains 8 lb of
acetaldehyde and 90 lb of toluene. Part of the acetaldehyde in
this solution is to be extracted using pure water as the extracting
agent. The extraction is to be performed in two stages, using 25
lb of fresh water for each stage. The raffinate layer from the first
stage is treated by fresh water in the second stage. The extraction
takes place at 170C and the equilibrium equation Y=2.2X may be
employed. Assuming toluene and water is immiscible, what would
be the weight percent of acetaldehyde in a mixture of the extracts
from both stage if each of the extraction were theoretically
perfect?
a. 8.96% c. 9.33%
b. 7.10% d. 5.52%
a. 8.96%
For numbers 33 to 34:
A solution of 5% acetaldehyde in toluene is to be extracted with
water in a five stage concurrent unit. If 25 kg water per 100 kg of
feed is used, calculate the following:
- The mass of acetaldehyde extracted if the equilibrium relation is
given by: kg acetaldehyde per kg water = 2.20 (kg acetaldehyde
per kg toluene).
a. 4.49 kg / 100 kg feed c. 3.36 kg / 100 kg feed
b. 1.11 kg / 100 kg feed d. 2.98 kg / 100 kg feed - The final concentration
a. 0.89% c. 0.54%
b. 0.67% d. 0.33%
a. 4.49 kg / 100 kg feed
c. 0.54%
A liquid mixture of ethyl alcohol and water is in equilibrium with a
vapor containing ethyl alcohol and water at a total pressure of 760
mmHg. A sample of the vapor indicates that it contains 3.3 mol of
ethyl alcohol for every 1.7 mol of water. If the liquid has a mol
fraction of 0.52 ethyl, what is the relative volatility for the mixture?
a.1.59 c. 1.69
b.1.79 d. 1.89
b.1.79
An equimolal mixture of benzene and toluene is subjected to flash
distillation at a separator pressure of 1 atm. If 40% of the charge
is vaporized, at what temperature will the vapor and liquid
separate?
a. 76.50C c. 950C
b. 82.100C d. 1060C
c. 950C
A mixture of 60 mole % A and 40 mol % B is subject to flash
distillation at a separator pressure of 1 atm. The relative volatility
of A with respect to B is constant 3. What fraction of the feed must
be vaporized to have the composition of the vapor leaving the
separator be 75 mol % A?
a. 0.3 c. 0.5
b. 0.6 d. 0.4
d. 0.4
Glycerin is steam distilled at 1820C and under a 26 in Hg vacuum.
A test shows that one lb of steam is consumed per lb of glycerine
distilled. What percent excess steam is actually used than
theoretical? Vapor pressure of glycerine at 1820C is 21 mmHg.
a. 37% c. 16%
b. 21% d. 54%
a. 37%
A benzene-toluene feed with (40 mol% benzene and 60 mol%
benzene) to a distillation column is at a temperature of 200C. The
molar heat capacity of the feed is 159.2 kJ/kmol-K. Molar latent
heats of vaporization of benzene and toluene are 30 813 and 33
325 kJ/kmol, respectively. The bubble point of the mixture is 95
0C. The slope of the q line is closest to
a. 0 c. 3.7
b. 1 d. -3.7
c. 3.7
A binary mixture with components A and B is to be separated in
a distillation column to obtain 95 mol% A as the top product. The
binary mixture has a constant relative volatility of 2. The
column feed is a saturated liquid containing 50 mol% A. Under
the usual simplifying assumptions such as constant molal
overflow, negligible heat loss, ideal trays, the minimum reflux ratio
for this separation is
a. 1.7 c. 1.4
b. 1.6 d. 1.5
a. 1.7
