Transcript 幻灯片 1 - qust.edu.cn

Chapter2
Thermodynamics of Separation
Operations
Exercises
Exercise2.1
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MutuaJ solubility data for the ispOctane (l)/furfural(2)
system "at 25°C are [Chem. Eng. ScL, 6, 116 (1957)]
Liquid Phase Ⅰ
Liquid PhaseⅡ
x1
0.0431
0.9461
Compute:
(a) The distribution coefficients for isooctane and furfural
(b) The relative selectivity for isooctane relative to furfural
(c) The activity coefficient of isooctane in liquid phase 1
and the activity coefficient of furfural in liquid phase 2
assuming γ(1)2 =1.0 and γ(2)1 =1.0
Exercise2.2
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A binary ideal gas mixture of A and B undergoes an isothermal
separation at T0, the infinite surroundings temperature. Starting with
Eq. (4), Table 2.1, derive an equation for the minimum work of
separation, Wmin, in terms of mole fractions of the feed and the two
products. Use your equation to prepare a plot of the dimensionless
group, Wmin/RTonF, as a function of mole fraction of A in the feed for:
(a) A perfect separation
(b) A separation with SFA = 0.98, SFB = 0.02
(c) A separation with SRA =9.0 and SRB = 1/9
(d) A separation with SF = 0.95 for A and SPA.B = 361
How sensitive is Wmin to product purities? Does Wmin depend on the
particular separation operation used?
Prove, by calculus, that the largest value of Wmin occurs for a feed
with equimolar quantities of A and B.
Exercise2.3
 A hydrocarbon
vapor-liquid mixture at
250°F and 500 psia contains N2, H2S,
CO2, and all the normal paraffins'^ from
methane to heptane. Use Figure 2.8 to
estimate the K-value of each component in
the mixture. Which components will have a
tendency to be present to a greater extent in
the equilibrium vapor?
Exercise2.4
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Use the R-K equation of state to estimate
the partial fugacity coefficients of propane
and benzene in the vapor mixture of
Example 2.5.
Exercise2.5
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Use a computer-aided, steady-state simulation program to
estimate the k-values, using the P-R or S-R-K equation of
state, of an equimolar mixture of the two butane isomers
and the four butene isomers at 220°F and 276.5 psia.
Compare these values with the following experimental
results [J. Chem. Eng. Data, 7, 331 (1962)]:
Component
K-value
Isobutane
1.067
Isobutene
1.024
n-Butane
0.922
1-Butene
1.024
trans-2-Butene 0.952
cis-2-Butene
0.876
Exercise2.6
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For the binary system ethanol(l)/isooctane(2) at 50°C, the infinitedilution, liquid-phase activity coefficients are
γ1 *=21.17 andγ2 *= 9.84.
(a) Calculate the constants A12and A21in the van Laar equations.
(b) Calculate the constants andin the Wilson equations.
(c) Using the constants from (a) and (b), calculated γ1 and γ2 over the
entire composition range and plot the calculated points as logγ versus
x1.
(d) How well do the van Laar and Wilson predictions agree with the
azeotropic point where x1= 0.5941,γ1 = 1.44, and γ2 = 2.18?
(e) Show that the van Laar equation erroneously predicts separation
into two liquid phases over a portion of the composition range by
calculating and plotting a y-x diagram like Figure 2.22.