Page 194 - Separation process principles 2

Exercises 159

(101.3 kPa) are presented below. 4.56 Repeat Example 4.10, except determine the temperature
necessary to crystallize 80% of the naphthalene.
(a) One hundred kilograms of a 30 wt% A-W solution is contacted
with 120 kg of ether in an equilibrium stage. What are the compo- 4.57 A total of 10,000 kg41 of a 10 wt% liquid solution of naph-
,itions and weights of the resulting extract and raffinate? What thalene in benzene is cooled from 30°C to 0°C. Assuming that equi-
would be the concentration of acid in the (ether-rich) extract if all librium is achieved, determine the amount of crystals formed and
the ether were removed? the composition and flow rate of the mother liquid. Are the crystals
benzene or naphthalene? Use Figure 4.23.
(b) A mixture containing 52 kg A and 48 kg W is contacted with
40 kg of E. What are the extract and raffinate compositions and 4.58 Repeat Example 4.11, except let the original solution be
quantities? 20 wt% Na2S04.
4.59 At 20°C, 1,000 kg of a mixture of 50 wt% Na2S04 . 10H20
LIQUID-LIQUID EQUILIBRIUM DATA FOR ACETIC
and 50 wt% Na2S04 crystals exists. How many kilograms of water
ACID (A), WATER (W), AND ISOPROPANOL ETHER (E)
must be added to just completely dissolve the crystals if the
AT 25°C AND 1 ATM
temperature is kept at 20°C and equilibrium is maintained? Use
Water-Rich Layer Ether-Rich Layer Figure 4.24.
wt%A Wt%W Wt%E Wt%A Wt%W Wt%E 4.60 Repeat Example 4.12, except determine the grams of acti-
vated carbon to achieve:
(a) 75% adsorption of phenol.
(b) 90% adsorption of phenol.
(c) 98% adsorption of phenol.
4.61 A colored substance (B) is to be removed from a mineral oil
by adsorption with clay particles at 25°C. The original oil has a
color index of 200 units1100 kg oil, while the decolorized oil must
have an index of only 20 units1100 kg oil. The following experi-
mental adsorption equilibrium data have been measured in a
Section 4.6
laboratory:
4.50 Diethylene glycol (DEG) is used as a solvent in the UDEX
cg, color units1 200 100 60 40 10
liquid-liquid extraction process [H.W. Grote, Chem Eng. Progr ,54
100 kg oil
(8), 43 (1958)l to separate paraffins from aromatics. If280 lbmolh
of 42.86 mol% n-hexane, 28.57 mol% n-heptane, 17.86 mol% ben- q~, color units1 10 7.0 5.4 4.4 2.2
zene, and 10.71 mol% toluene is contacted with 500 lbmolh of 100 kg clay
90 mol% aqueous DEG at 325°F and 300 psia, calculate, using a (a) Fit the data to the Freundlich equation.
simulation computer program and the UNIFAC Ln method for es-
(b) Compute the kilograms of clay needed to treat 500 kg of oil if
timating liquid-phase activity coefficients, the flow rates and molar one equilibrium contact is used.
compositions of the resulting two liquid phases. Is DEG more
selective for the paraffins or the aromatics?
Section 4.8
4.51 A feed of 110 lbmolh includes 5, 3, and 2 lbmolh, respec-
tively, of formic acid, acetic acid, and propionic acid in water. If the 4.62 Vapor-liquid equilibrium data in mole fractions for the
acids are extracted in a single equilibrium stage with 100 lbmolh system acetone-air-water at 1 atm (101.3 kPa) are as follows:
of ethyl acetate (EA), calculate with a simulation computer pro-
y, acetone in air: 0.004 0.008 0.014 0.017 0.019 0.020
gram using the UNIFAC method, flow rates and molar composi-
x, acetonein water: 0.002 0.004 0.006 0.008 0.010 0.012
tions of the resulting two liquid phases. What is the order of selec-
tivity of EA for the three organic acids? (a) Plot the data as (1) a graph of moles acetone per mole air ver-
sus moles acetone per mole water, (2) partial pressure of acetone
Section 4.7
versus g acetone per g water, and (3) y versus x.
4.52 Repeat Example 4.9 for 200,000 kglh of hexane. (b) If 20 moles of gas containing 0.015 mole fraction acetone is
4.53 Water is to be used in a single equilibrium stage to dissolve brought into contact with 15 moles of water in an equilibrium stage,
1,350 kg/h of Na2C03 from 3,750 kglh of a solid, where the bal- what would be the composition of the discharge streams? Solve
ance is an insoluble oxide. If 4,000 kg/h of water is used and the graphically. For both parts, neglect partitioning of water and air.
underflow from the stage is 40 wt% solvent on a solute-free basis, 4.63 It has been proposed that oxygen be separated from nitro-
compute the flow rates and compositions of the overflow and the gen by absorbing and desorbing air in water. Pressures from 101.3
underflow. to 10,130 kPa and temperatures between 0 and 100°C are to be
4.54 Repeat Exercise 4.53 if the residence time is only sufficient used.
to leach 80% of the carbonate. (a) Devise a workable scheme for doing the separation assuming
4.55 A total of 6,000 lb/h of a liquid solution of 40 wt% benzene the air is 79 mol% N2 and 21 mol% 02.
in naphthalene at 50°C is cooled to 15°C. Assuming that equilib- (b) Henry's law constants for O2 and N2 are given in Figure 4.27.
rium is achieved, use Figure 4.23 to determine the amount of crys- How many batch absorption steps would be necessary to make
tals formed, and the flow rate and composition of the mother liquor. 90 mol% pure oxygen? What yield of oxygen (based on total
Are the crystals benzene or naphthalene? amount of oxygen feed) would be obtained?