Page 193 - Separation process principles 2

158 Chapter 4 Single Equilibrium Stages and Flash Calculations

1 wt% acetic acid. The following four solvents, with accompanying
distribution coefficients in mass-fraction units, are being consid-
ered. Water and each solvent (C) can be considered immiscible. For
Bubble-point feed, 160 kmollh - IFt each solvent, estimate the kilograms required per hour if a single
- I
equilibrium stage is used.
Mole percent
C, 20
nC, 40 Solvent KD
nC, 50
Methyl acetate 1.273
Composition, mol% Isopropyl ether 0.429
Stream Total flow rate kmollh C3 nC4 nC5 Heptadecanol 0.312
Chloroform 0.178

4.46 Forty-five kilograms of a solution containing 30 wt% ethyl-
Figure 4.43 Conditions for Exercise 4.41. ene glycol in water is to be extracted with furfural. Using Figures
4.14a and 4.14e, calculate:
(a) The minimum quantity of solvent.
4.41 Streams entering stage F of a distillation column are shown (b) The maximum quantity of solvent.
in Figure 4.43. What is the temperature of stage F and the compo-
(c) The weights of solvent-free extract and raffinate for 45 kg sol-
sitions and amounts of streams VF and LF if the pressure is 785 kPa vent, and the percent glycol extracted.
for all streams? Use a simulation computer program to obtain the
(d) The maximum possible purity of glycol in the finished extract
answers.
and the maximum purity of water in the raffinate for one equilib-
4.42 Flash adiabatically, across a valve, a stream composed of rium stage.
the six hydrocarbons given below. The feed upstream of the valve
4.47 Prove that, in a triangular diagram, where each vertex repre-
is at 250°F and 500 psia. The pressure downstream of the valve is
sents a pure component, the composition of the system at any point
300 psia.
inside the triangle is proportional to the length of the respective
perpendicular drawn from the point to the side of the triangle op-
Component Zi
posite the vertex in question. It is not necessary to assume a special
case (i.e., a right or equilateral triangle).
4.48 A mixture of chloroform (CHC13) and acetic acid at 18OC
and 1 atm (101.3 kPa) is to be extracted with water to recover
the acid.
(a) Forty-five kilograms of a mixture containing 35 wt% CHC13
and 65 wt% acid is treated with 22.75 kg of water at 18OC in a sim-
Compute using a simulation computer program: ple one-stage batch extraction. What are the compositions and
(a) The phase condition upstream of the valve. weights of the raffinate and extract layers produced?
(b) The temperature downstream of the valve. (b) If the raffinate layer from the above treatment is extracted
(c) The molar fraction vaporized downstream of the valve. again with one-half its weight of water, what will be the composi-
tions and weights of the new layers?
(d) The mole fraction compositions of the vapor and liquid phases
downstream of the valve. (c) If all the water is removed from this final raffinate layer, what
will its composition be?
4.43 Propose a detailed algorithm like Figure 4.19a and Table 4.4
for a flash where the percent vaporized and the flash pressure are to Solve this exercise using the following equilibrium data to con-
be specified. struct one or more of the types of diagrams in Figure 4.14.
4.44 Determine algorithms for carrying out the following flash
calculations, assuming that expressions for K-values and enthalpies LIQUID-LIQUID EQUILIBRIUM DATA FOR
are available. CHClj-HzO-CH3COOH AT 18°C AND 1 ATM

Given Find Heavy Phase (wt%) Light Phase (wt%)
CHClj HzO CH3COOH
0.84 99.16 0.00
1.21 73.69 25.10
7.30 48.58 44.12
15.11 34.71 50.18
18.33 31.11 50.56
Section 4.5 25.20 25.39 49.4.1
28.85 23.28 47.87 i
4.45 A feed of 13,500 kgh consists of 8 wt% acetic acid (B) in 1
water (A). The removal of the acetic acid is to be accomplished 4.49 Isopropyl ether (E) is used to separate acetic acid (A) from
by liquid-liquid extraction at 25OC. The raffinate is to contain only water (W). The liquid-liquid equilibrium data at 25OC and 1 atm